21172018648 has 24 divisors (see below), whose sum is σ = 43309193940. Its totient is φ = 9623024400.

The previous prime is 21172018589. The next prime is 21172018667. The reversal of 21172018648 is 84681027112.

It is a self number, because there is not a number n which added to its sum of digits gives 21172018648.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1357213 + ... + 1372723.

Almost surely, 2^21172018648 is an apocalyptic number.

It is an amenable number.

21172018648 is an abundant number, since it is smaller than the sum of its proper divisors (22137175292).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21172018648 is an frugal number, since it uses more digits than its factorization.

21172018648 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31039 (or 15524 counting only the distinct ones).

The product of its (nonzero) digits is 43008, while the sum is 40.

The spelling of 21172018648 in words is "twenty-one billion, one hundred seventy-two million, eighteen thousand, six hundred forty-eight".