21976656 has 80 divisors (see below), whose sum is σ = 62704320. Its totient is φ = 6589440.

The previous prime is 21976639. The next prime is 21976667. The reversal of 21976656 is 65667912.

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25155 + ... + 26013.

It is an arithmetic number, because the mean of its divisors is an integer number (783804).

Almost surely, 2^21976656 is an apocalyptic number.

21976656 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21976656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31352160).

21976656 is an abundant number, since it is smaller than the sum of its proper divisors (40727664).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21976656 is a wasteful number, since it uses less digits than its factorization.

21976656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 924 (or 918 counting only the distinct ones).

The product of its digits is 136080, while the sum is 42.

The square root of 21976656 is about 4687.9266205861. The cubic root of 21976656 is about 280.1047907089.

The spelling of 21976656 in words is "twenty-one million, nine hundred seventy-six thousand, six hundred fifty-six".