21255315520 has 28 divisors (see below), whose sum is σ = 50614220844. Its totient is φ = 8502126080.

The previous prime is 21255315493. The next prime is 21255315541. The reversal of 21255315520 is 2551355212.

It can be written as a sum of positive squares in 2 ways, for example, as 16964541504 + 4290774016 = 130248^2 + 65504^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33211111 + ... + 33211750.

Almost surely, 2^21255315520 is an apocalyptic number.

21255315520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21255315520 is an abundant number, since it is smaller than the sum of its proper divisors (29358905324).

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

21255315520 is an equidigital number, since it uses as much as digits as its factorization.

21255315520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66422878 (or 66422868 counting only the distinct ones).

The product of its (nonzero) digits is 15000, while the sum is 31.

The spelling of 21255315520 in words is "twenty-one billion, two hundred fifty-five million, three hundred fifteen thousand, five hundred twenty".