21643944 has 32 divisors (see below), whose sum is σ = 61840320. Its totient is φ = 6183936.

The previous prime is 21643939. The next prime is 21643961. The reversal of 21643944 is 44934612.

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, 64249 + ... + 64584.

It is an arithmetic number, because the mean of its divisors is an integer number (1932510).

Almost surely, 2^21643944 is an apocalyptic number.

21643944 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21643944 is an abundant number, since it is smaller than the sum of its proper divisors (40196376).

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

21643944 is a wasteful number, since it uses less digits than its factorization.

21643944 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128849 (or 128845 counting only the distinct ones).

The product of its digits is 20736, while the sum is 33.

The square root of 21643944 is about 4652.3052350421. The cubic root of 21643944 is about 278.6840631778.

The spelling of 21643944 in words is "twenty-one million, six hundred forty-three thousand, nine hundred forty-four".