21390180921 has 32 divisors (see below), whose sum is σ = 32146523520. Its totient is φ = 14054591232.

The previous prime is 21390180871. The next prime is 21390180949. The reversal of 21390180921 is 12908109312.

21390180921 is a `hidden beast` number, since 2 + 1 + 390 + 180 + 92 + 1 = 666.

It is not a de Polignac number, because 21390180921 - 2³⁴ = 4210311737 is a prime.

It is a super-2 number, since 2×21390180921² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21390180961) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3519141 + ... + 3525213.

It is an arithmetic number, because the mean of its divisors is an integer number (1004578860).

Almost surely, 2^21390180921 is an apocalyptic number.

It is an amenable number.

21390180921 is a deficient number, since it is larger than the sum of its proper divisors (10756342599).

21390180921 is a wasteful number, since it uses less digits than its factorization.

21390180921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7942 (or 7936 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 36.

The spelling of 21390180921 in words is "twenty-one billion, three hundred ninety million, one hundred eighty thousand, nine hundred twenty-one".