21646920 has 32 divisors (see below), whose sum is σ = 64941120. Its totient is φ = 5772480.

The previous prime is 21646913. The next prime is 21646921. The reversal of 21646920 is 2964612.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is not an unprimeable number, because it can be changed into a prime (21646921) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 90076 + ... + 90315.

It is an arithmetic number, because the mean of its divisors is an integer number (2029410).

Almost surely, 2^21646920 is an apocalyptic number.

21646920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21646920 is an abundant number, since it is smaller than the sum of its proper divisors (43294200).

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

21646920 is a wasteful number, since it uses less digits than its factorization.

21646920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 180405 (or 180401 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 30.

The square root of 21646920 is about 4652.6250654872. The cubic root of 21646920 is about 278.6968354305.

The spelling of 21646920 in words is "twenty-one million, six hundred forty-six thousand, nine hundred twenty".