21565523655 has 96 divisors (see below), whose sum is σ = 42751328256. Its totient is φ = 9962422272.

The previous prime is 21565523633. The next prime is 21565523657. The reversal of 21565523655 is 55632556512.

21565523655 is a `hidden beast` number, since 2 + 1 + 5 + 65 + 523 + 65 + 5 = 666.

It is not a de Polignac number, because 21565523655 - 2¹⁶ = 21565458119 is a prime.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 21565523655.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21565523657) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 3507514 + ... + 3513656.

It is an arithmetic number, because the mean of its divisors is an integer number (445326336).

Almost surely, 2^21565523655 is an apocalyptic number.

21565523655 is a deficient number, since it is larger than the sum of its proper divisors (21185804601).

21565523655 is a wasteful number, since it uses less digits than its factorization.

21565523655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6537 (or 6534 counting only the distinct ones).

The product of its digits is 1350000, while the sum is 45.

The spelling of 21565523655 in words is "twenty-one billion, five hundred sixty-five million, five hundred twenty-three thousand, six hundred fifty-five".