18744621921 has 27 divisors (see below), whose sum is σ = 27692417233. Its totient is φ = 12217937640.

The previous prime is 18744621899. The next prime is 18744621937. The reversal of 18744621921 is 12912644781.

The square root of 18744621921 is 136911.

It is a perfect power (a square), and thus also a powerful number.

18744621921 is a `hidden beast` number, since 18 + 7 + 4 + 4 + 621 + 9 + 2 + 1 = 666.

It is not a de Polignac number, because 18744621921 - 2¹⁵ = 18744589153 is a prime.

It is a super-2 number, since 2×18744621921² (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 (18744623921) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 19303966 + ... + 19304936.

Almost surely, 2^18744621921 is an apocalyptic number.

18744621921 is the 136911-st square number.

18744621921 is the 68456-th centered octagonal number.

It is an amenable number.

18744621921 is a deficient number, since it is larger than the sum of its proper divisors (8947795312).

18744621921 is an frugal number, since it uses more digits than its factorization.

18744621921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2042 (or 1021 counting only the distinct ones).

The product of its digits is 193536, while the sum is 45.

The spelling of 18744621921 in words is "eighteen billion, seven hundred forty-four million, six hundred twenty-one thousand, nine hundred twenty-one".