21157773658564 has 81 divisors (see below), whose sum is σ = 40027631514087. Its totient is φ = 9783574871808.

The previous prime is 21157773658523. The next prime is 21157773658579. The reversal of 21157773658564 is 46585637775112.

The square root of 21157773658564 is 4599758.

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

It can be written as a sum of positive squares in 4 ways, for example, as 131146828164 + 21026626830400 = 362142^2 + 4585480^2 .

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21157773658564.

It is an unprimeable number.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 9227113402 + ... + 9227115694.

Almost surely, 2^{21157773658564} is an apocalyptic number.

21157773658564 is the 4599758-th square number.

It is an amenable number.

21157773658564 is a deficient number, since it is larger than the sum of its proper divisors (18869857855523).

21157773658564 is an frugal number, since it uses more digits than its factorization.

21157773658564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4742 (or 2371 counting only the distinct ones).

The product of its digits is 296352000, while the sum is 67.

The spelling of 21157773658564 in words is "twenty-one trillion, one hundred fifty-seven billion, seven hundred seventy-three million, six hundred fifty-eight thousand, five hundred sixty-four".