21653621523 has 6 divisors (see below), whose sum is σ = 31277453324. Its totient is φ = 14435747676.

The previous prime is 21653621513. The next prime is 21653621557. The reversal of 21653621523 is 32512635612.

21653621523 is a `hidden beast` number, since 2 + 1 + 6 + 5 + 3 + 621 + 5 + 23 = 666.

It is not a de Polignac number, because 21653621523 - 2¹⁷ = 21653490451 is a prime.

It is a super-2 number, since 2×21653621523² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21653621513) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1202978965 + ... + 1202978982.

Almost surely, 2^21653621523 is an apocalyptic number.

21653621523 is a deficient number, since it is larger than the sum of its proper divisors (9623831801).

21653621523 is a wasteful number, since it uses less digits than its factorization.

21653621523 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2405957953 (or 2405957950 counting only the distinct ones).

The product of its digits is 64800, while the sum is 36.

The spelling of 21653621523 in words is "twenty-one billion, six hundred fifty-three million, six hundred twenty-one thousand, five hundred twenty-three".