21631766 has 16 divisors (see below), whose sum is σ = 36783600. Its totient is φ = 9458208.

The previous prime is 21631739. The next prime is 21631777. The reversal of 21631766 is 66713612.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21401 + ... + 22388.

It is an arithmetic number, because the mean of its divisors is an integer number (2298975).

Almost surely, 2^21631766 is an apocalyptic number.

21631766 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21631766 is a deficient number, since it is larger than the sum of its proper divisors (15151834).

21631766 is a wasteful number, since it uses less digits than its factorization.

21631766 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43823.

The product of its digits is 9072, while the sum is 32.

The square root of 21631766 is about 4650.9962373668. The cubic root of 21631766 is about 278.6317860261.

The spelling of 21631766 in words is "twenty-one million, six hundred thirty-one thousand, seven hundred sixty-six".