21976640 has 56 divisors (see below), whose sum is σ = 59813952. Its totient is φ = 7534080.

The previous prime is 21976639. The next prime is 21976667. The reversal of 21976640 is 4667912.

It is a tau number, because it is divible by the number of its divisors (56).

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a self number, because there is not a number n which added to its sum of digits gives 21976640.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 2666 + ... + 7145.

Almost surely, 2^21976640 is an apocalyptic number.

21976640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21976640 is an abundant number, since it is smaller than the sum of its proper divisors (37837312).

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

21976640 is an equidigital number, since it uses as much as digits as its factorization.

21976640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9835 (or 9825 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 35.

The square root of 21976640 is about 4687.9249140745. The cubic root of 21976640 is about 280.1047227326.

The spelling of 21976640 in words is "twenty-one million, nine hundred seventy-six thousand, six hundred forty".