2315515721 has 4 divisors (see below), whose sum is σ = 2316335892. Its totient is φ = 2314695552.

The previous prime is 2315515703. The next prime is 2315515723. The reversal of 2315515721 is 1275155132.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1860973321 + 454542400 = 43139^2 + 21320^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2315515721 is a prime.

It is a super-2 number, since 2×2315515721² = 10723226108396299682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2315515723) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 405836 + ... + 411501.

It is an arithmetic number, because the mean of its divisors is an integer number (579083973).

Almost surely, 2^2315515721 is an apocalyptic number.

It is an amenable number.

2315515721 is a deficient number, since it is larger than the sum of its proper divisors (820171).

2315515721 is an equidigital number, since it uses as much as digits as its factorization.

2315515721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 820170.

The product of its digits is 10500, while the sum is 32.

The square root of 2315515721 is about 48119.8059119112. The cubic root of 2315515721 is about 1322.9677108060.

The spelling of 2315515721 in words is "two billion, three hundred fifteen million, five hundred fifteen thousand, seven hundred twenty-one".