21964840 has 16 divisors (see below), whose sum is σ = 49420980. Its totient is φ = 8785920.

The previous prime is 21964837. The next prime is 21964903. The reversal of 21964840 is 4846912.

It can be written as a sum of positive squares in 2 ways, for example, as 20412324 + 1552516 = 4518^2 + 1246^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21964796 and 21964805.

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, 274521 + ... + 274600.

Almost surely, 2^21964840 is an apocalyptic number.

21964840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21964840 is an abundant number, since it is smaller than the sum of its proper divisors (27456140).

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

21964840 is a wasteful number, since it uses less digits than its factorization.

21964840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 549132 (or 549128 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 34.

The square root of 21964840 is about 4686.6661925083. Note that the first 3 decimals coincide. The cubic root of 21964840 is about 280.0545811964.

The spelling of 21964840 in words is "twenty-one million, nine hundred sixty-four thousand, eight hundred forty".