21065619600 has 405 divisors, whose sum is σ = 76221579499. Its totient is φ = 5387596800.

The previous prime is 21065619593. The next prime is 21065619629. The reversal of 21065619600 is 691656012.

The square root of 21065619600 is 145140.

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

21065619600 is a `hidden beast` number, since 2 + 1 + 0 + 6 + 561 + 96 + 0 + 0 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 8866858896 + 12198760704 = 94164^2 + 110448^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 357044371 + ... + 357044429.

Almost surely, 2^21065619600 is an apocalyptic number.

21065619600 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

21065619600 is the 145140-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21065619600

21065619600 is an abundant number, since it is smaller than the sum of its proper divisors (55155959899).

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

21065619600 is a wasteful number, since it uses less digits than its factorization.

21065619600 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 224 (or 110 counting only the distinct ones).

The product of its (nonzero) digits is 19440, while the sum is 36.

Multiplying 21065619600 by its sum of digits (36), we get a square (758362305600 = 870840²).

21065619600 divided by its sum of digits (36) gives a square (585156100 = 24190²).

The spelling of 21065619600 in words is "twenty-one billion, sixty-five million, six hundred nineteen thousand, six hundred".