21315540520520 has 16 divisors (see below), whose sum is σ = 47959966171260. Its totient is φ = 8526216208192.

The previous prime is 21315540520489. The next prime is 21315540520577. The reversal of 21315540520520 is 2502504551312.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 17782802245156 + 3532738275364 = 4216966^2 + 1879558^2 .

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, 266444256467 + ... + 266444256546.

Almost surely, 2^{21315540520520} is an apocalyptic number.

21315540520520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21315540520520 is an abundant number, since it is smaller than the sum of its proper divisors (26644425650740).

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

21315540520520 is a wasteful number, since it uses less digits than its factorization.

21315540520520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 532888513024 (or 532888513020 counting only the distinct ones).

The product of its (nonzero) digits is 60000, while the sum is 35.

The spelling of 21315540520520 in words is "twenty-one trillion, three hundred fifteen billion, five hundred forty million, five hundred twenty thousand, five hundred twenty".