21972651 has 16 divisors (see below), whose sum is σ = 29872128. Its totient is φ = 14364000.

The previous prime is 21972649. The next prime is 21972661. The reversal of 21972651 is 15627912.

It is not a de Polignac number, because 21972651 - 2¹ = 21972649 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21972611) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 38196 + ... + 38766.

It is an arithmetic number, because the mean of its divisors is an integer number (1867008).

Almost surely, 2^21972651 is an apocalyptic number.

21972651 is a deficient number, since it is larger than the sum of its proper divisors (7899477).

21972651 is a wasteful number, since it uses less digits than its factorization.

21972651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 802.

The product of its digits is 7560, while the sum is 33.

The square root of 21972651 is about 4687.4994400000. The cubic root of 21972651 is about 280.0877743524.

The spelling of 21972651 in words is "twenty-one million, nine hundred seventy-two thousand, six hundred fifty-one".