21500566553 has 16 divisors (see below), whose sum is σ = 23550912000. Its totient is φ = 19540358400.

The previous prime is 21500566523. The next prime is 21500566559. The reversal of 21500566553 is 35566500512.

It is a cyclic number.

It is not a de Polignac number, because 21500566553 - 2¹⁸ = 21500304409 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21500566559) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 198698 + ... + 287196.

It is an arithmetic number, because the mean of its divisors is an integer number (1471932000).

Almost surely, 2^21500566553 is an apocalyptic number.

It is an amenable number.

21500566553 is a deficient number, since it is larger than the sum of its proper divisors (2050345447).

21500566553 is a wasteful number, since it uses less digits than its factorization.

21500566553 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89008.

The product of its (nonzero) digits is 135000, while the sum is 38.

The spelling of 21500566553 in words is "twenty-one billion, five hundred million, five hundred sixty-six thousand, five hundred fifty-three".