21311512520 has 32 divisors (see below), whose sum is σ = 48023505720. Its totient is φ = 8511697920.

The previous prime is 21311512517. The next prime is 21311512561. The reversal of 21311512520 is 2521511312.

It can be written as a sum of positive squares in 4 ways, for example, as 18743252836 + 2568259684 = 136906^2 + 50678^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 376577 + ... + 429456.

Almost surely, 2^21311512520 is an apocalyptic number.

21311512520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21311512520 is an abundant number, since it is smaller than the sum of its proper divisors (26711993200).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21311512520 is a wasteful number, since it uses less digits than its factorization.

21311512520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 806705 (or 806701 counting only the distinct ones).

The product of its (nonzero) digits is 600, while the sum is 23.

The spelling of 21311512520 in words is "twenty-one billion, three hundred eleven million, five hundred twelve thousand, five hundred twenty".