21391976 has 16 divisors (see below), whose sum is σ = 40171140. Its totient is φ = 10679680.

The previous prime is 21391949. The next prime is 21391987. The reversal of 21391976 is 67919312.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 21252100 + 139876 = 4610^2 + 374^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4940 + ... + 8196.

Almost surely, 2^21391976 is an apocalyptic number.

It is an amenable number.

21391976 is a deficient number, since it is larger than the sum of its proper divisors (18779164).

21391976 is a wasteful number, since it uses less digits than its factorization.

21391976 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4084 (or 4080 counting only the distinct ones).

The product of its digits is 20412, while the sum is 38.

The square root of 21391976 is about 4625.1460517480. The cubic root of 21391976 is about 277.5984057025.

The spelling of 21391976 in words is "twenty-one million, three hundred ninety-one thousand, nine hundred seventy-six".