21639974 has 32 divisors (see below), whose sum is σ = 35964000. Its totient is φ = 9725184.

The previous prime is 21639967. The next prime is 21639977. The reversal of 21639974 is 47993612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21639977) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 80312 + ... + 80580.

It is an arithmetic number, because the mean of its divisors is an integer number (1123875).

Almost surely, 2^21639974 is an apocalyptic number.

21639974 is a deficient number, since it is larger than the sum of its proper divisors (14324026).

21639974 is a wasteful number, since it uses less digits than its factorization.

21639974 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 392.

The product of its digits is 81648, while the sum is 41.

The square root of 21639974 is about 4651.8785452761. The cubic root of 21639974 is about 278.6670231014.

The spelling of 21639974 in words is "twenty-one million, six hundred thirty-nine thousand, nine hundred seventy-four".