21939651 has 12 divisors (see below), whose sum is σ = 31894512. Its totient is φ = 14532336.

The previous prime is 21939649. The next prime is 21939653. The reversal of 21939651 is 15693912.

21939651 is a `hidden beast` number, since 219 + 396 + 51 = 666.

It is an interprime number because it is at equal distance from previous prime (21939649) and next prime (21939653).

It is not a de Polignac number, because 21939651 - 2¹ = 21939649 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21939653) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6351 + ... + 9176.

It is an arithmetic number, because the mean of its divisors is an integer number (2657876).

Almost surely, 2^21939651 is an apocalyptic number.

21939651 is a deficient number, since it is larger than the sum of its proper divisors (9954861).

21939651 is a wasteful number, since it uses less digits than its factorization.

21939651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15690 (or 15687 counting only the distinct ones).

The product of its digits is 14580, while the sum is 36.

The square root of 21939651 is about 4683.9781169429. The cubic root of 21939651 is about 279.9474858999.

The spelling of 21939651 in words is "twenty-one million, nine hundred thirty-nine thousand, six hundred fifty-one".