21009975664896 has 405 divisors, whose sum is σ = 63378650396061. Its totient is φ = 6922579396608.

The previous prime is 21009975664861. The next prime is 21009975664907. The reversal of 21009975664896 is 69846657990012.

The square root of 21009975664896 is 4583664.

It is a perfect power (a square), and thus also a powerful number.

21009975664896 is a `hidden beast` number, since 2 + 1 + 0 + 0 + 9 + 97 + 56 + 6 + 489 + 6 = 666.

It can be written as a sum of positive squares in only one way, i.e., 19567670743296 + 1442304921600 = 4423536^2 + 1200960^2 .

It is a Harshad number since it is a multiple of its sum of digits (72).

It is an unprimeable number.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 91746618510 + ... + 91746618738.

Almost surely, 2^{21009975664896} is an apocalyptic number.

21009975664896 is the 4583664-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21009975664896

21009975664896 is an abundant number, since it is smaller than the sum of its proper divisors (42368674731165).

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

21009975664896 is an frugal number, since it uses more digits than its factorization.

21009975664896 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 764 (or 373 counting only the distinct ones).

The product of its (nonzero) digits is 352719360, while the sum is 72.

The spelling of 21009975664896 in words is "twenty-one trillion, nine billion, nine hundred seventy-five million, six hundred sixty-four thousand, eight hundred ninety-six".