Let
(1)

be the sum of the first primes (i.e., the sum analog of the primorial function). The first few terms are 2, 5, 10, 17, 28, 41, 58, 77, ... (OEIS A007504). Bach and Shallit (1996) show that
(2)

and provide a general technique for estimating such sums.
The first few values of such that is prime are 1, 2, 4, 6, 12, 14, 60, 64, 96, 100, ... (OEIS A013916). The corresponding values of are 2, 5, 17, 41, 197, 281, 7699, 8893, 22039, 24133, ... (OEIS A013918).
The first few values of such that are 1, 23, 53, 853, 11869, 117267, 339615, 3600489, 96643287, ... (OEIS A045345). The corresponding values of are 2, 874, 5830, 2615298, 712377380, 86810649294, 794712005370, 105784534314378, 92542301212047102, ... (OEIS A050247; Rivera), and the values of are 2, 38, 110, 3066, 60020, 740282, 2340038, 29380602, 957565746, ... (OEIS A050248; Rivera).
In 1737, Euler showed that the harmonic series of primes, (i.e., sum of the reciprocals of the primes) diverges
(3)

(Nagell 1951, p. 59; Hardy and Wright 1979, pp. 17 and 22), although it does so very slowly.
A rapidly converging series for the Mertens constant
(4)

is given by
(5)

where is the EulerMascheroni constant, is the Riemann zeta function, and is the Möbius function (Flajolet and Vardi 1996, Schroeder 1997, Knuth 1998).
Dirichlet showed the even stronger result that
(6)

(Davenport 1980, p. 34). Despite the divergence of the sum of reciprocal primes, the alternating series
(7)

(OEIS A078437) converges (Robinson and Potter 1971), but it is not known if the sum
(8)

does (Guy 1994, p. 203; Erdős 1998; Finch 2003).
There are also classes of sums of reciprocal primes with sign determined by congruences on , for example
(9)

(OEIS A086239), where
(10)

(Glaisher 1891b; Finch 2003; Jameson 2003, p. 177),
(11)

(OEIS A086240; Glaisher 1893, Finch 2003), and
(12)

(OEIS A086241), where
(13)

(Glaisher 1891c; Finch 2003; Jameson 2003, p. 177).
Although diverges, Brun (1919) showed that
(14)

where
(15)

(OEIS A065421) is Brun's constant.
The function defined by
(16)

taken over the primes converges for and is a generalization of the Riemann zeta function known as the prime zeta function.
Consider the positive integers with prime factorizations
(17)

such that there are an odd number of (not necessarily distinct) prime factors, i.e., is odd. The first few such numbers are 2, 3, 5, 7, 8, 11, 12, 13, 17, 18, 19, 20, 23, 27, 28, 29, ... (OEIS A026424). Then
(18)
 
(19)
 
(20)

(Gourdon and Sebah), where is the Riemann zeta function. The first few terms are then
(21)
 
(22)
 
(23)
 
(24)

Consider the analogous sum where, in addition, the terms included must have an odd number of distinct prime factors, i.e., is odd and . The first few such numbers are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 30, 31, 37, 41, 42, ... (OEIS A030059), which include the composite numbers 30, 42, 66, 70, 78, 102, ... (OEIS A093599). Then
(25)
 
(26)
 
(27)

(Gourdon and Sebah). The first few terms are then
(28)
 
(29)
 
(30)
 
(31)

The sum
(32)
 
(33)
 
(34)

(OEIS A086242) is also finite (Glaisher 1891a; Cohen; Finch 2003), where
(35)

is the totient function, and is the Riemann zeta function.
Some curious sums satisfied by primes include
(36)

giving the sequence 0, 2, 18, 60, 270, 462, 1080, ... (OEIS A078837; Doster 1993) for , 3, 5, ..., and
(37)

giving the sequence 0, 2, 30, 120, 630, 1122, 2760, ... (OEIS A078838; Doster 1993),
(38)

giving the sequence 0, 1, 12, 45, 225, 396, 960, 1377, ... (OEIS A331764; J.C. Babois, pers. comm., Jan. 31, 2021),
(39)
 
(40)

where is the Mangoldt function, and
(41)

(Berndt 1994, p. 114).
Let be the number of ways an integer can be written as a sum of two or more consecutive primes. For example, , so and , so . The sequence of values of for , 2, ... is given by 0, 0, 0, 0, 1, 0, 0, 1, 0, 1, 0, 1, ... (OEIS A084143). The following table gives the first few such that for small .
OEIS  values of such that  
1  A050936  5, 8, 10, 12, 15, 17, 18, 23, 24, 26, 28, 30, 31, 36, ... 
2  A067372  36, 41, 60, 72, 83, 90, 100, 112, 119, ... 
3  A067373  240, 287, 311, 340, 371, 510, 660, 803, ... 
Similarly, the following table gives the first few such that for small .
OEIS  values of such that  
1  A084146  5, 8, 10, 12, 15, 17, 18, 23, 24, 26, 28, 30, 31, 39, ... 
2  A084147  36, 41, 60, 72, 83, 90, 100, 112, 119, 120, 138, ... 
Now consider instead the number of ways in which a number can be represented as a sum of one or more consecutive primes (i.e., the same sequence as before but one larger for each prime number). Amazingly, it then turns out that
(42)

(Moser 1963; Le Lionnais 1983, p. 30).