21974812821 has 12 divisors (see below), whose sum is σ = 34183042348. Its totient is φ = 13522961664.

The previous prime is 21974812819. The next prime is 21974812829. The reversal of 21974812821 is 12821847912.

21974812821 is a `hidden beast` number, since 2 + 1 + 97 + 481 + 2 + 82 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 7484672196 + 14490140625 = 86514^2 + 120375^2 .

It is not a de Polignac number, because 21974812821 - 2¹ = 21974812819 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21974812829) 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, 93909340 + ... + 93909573.

Almost surely, 2^21974812821 is an apocalyptic number.

It is an amenable number.

21974812821 is a deficient number, since it is larger than the sum of its proper divisors (12208229527).

21974812821 is a wasteful number, since it uses less digits than its factorization.

21974812821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 187818932 (or 187818929 counting only the distinct ones).

The product of its digits is 129024, while the sum is 45.

The spelling of 21974812821 in words is "twenty-one billion, nine hundred seventy-four million, eight hundred twelve thousand, eight hundred twenty-one".