21516520400 has 30 divisors (see below), whose sum is σ = 51693441222. Its totient is φ = 8606608000.

The previous prime is 21516520369. The next prime is 21516520451. The reversal of 21516520400 is 402561512.

It can be written as a sum of positive squares in 3 ways, for example, as 2875533376 + 18640987024 = 53624^2 + 136532^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21516520400.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 26895251 + ... + 26896050.

Almost surely, 2^21516520400 is an apocalyptic number.

21516520400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21516520400 is an abundant number, since it is smaller than the sum of its proper divisors (30176920822).

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

21516520400 is a wasteful number, since it uses less digits than its factorization.

21516520400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53791319 (or 53791308 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 26.

The spelling of 21516520400 in words is "twenty-one billion, five hundred sixteen million, five hundred twenty thousand, four hundred".