21937640 has 16 divisors (see below), whose sum is σ = 49359780. Its totient is φ = 8775040.

The previous prime is 21937639. The next prime is 21937679. The reversal of 21937640 is 4673912.

It can be written as a sum of positive squares in 2 ways, for example, as 20232004 + 1705636 = 4498^2 + 1306^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21937597 and 21937606.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 274181 + ... + 274260.

Almost surely, 2^21937640 is an apocalyptic number.

21937640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21937640 is an abundant number, since it is smaller than the sum of its proper divisors (27422140).

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

21937640 is a wasteful number, since it uses less digits than its factorization.

21937640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 548452 (or 548448 counting only the distinct ones).

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

The square root of 21937640 is about 4683.7634440693. The cubic root of 21937640 is about 279.9389322604.

The spelling of 21937640 in words is "twenty-one million, nine hundred thirty-seven thousand, six hundred forty".