21172405653 has 12 divisors (see below), whose sum is σ = 34951272928. Its totient is φ = 12098517480.

The previous prime is 21172405651. The next prime is 21172405673. The reversal of 21172405653 is 35650427112.

21172405653 is a `hidden beast` number, since 21 + 1 + 72 + 4 + 0 + 565 + 3 = 666.

It is not a de Polignac number, because 21172405653 - 2¹ = 21172405651 is a prime.

It is a super-2 number, since 2×21172405653² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21172405651) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 168034903 + ... + 168035028.

Almost surely, 2^21172405653 is an apocalyptic number.

It is an amenable number.

21172405653 is a deficient number, since it is larger than the sum of its proper divisors (13778867275).

21172405653 is a wasteful number, since it uses less digits than its factorization.

21172405653 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 336069944 (or 336069941 counting only the distinct ones).

The product of its (nonzero) digits is 50400, while the sum is 36.

The spelling of 21172405653 in words is "twenty-one billion, one hundred seventy-two million, four hundred five thousand, six hundred fifty-three".