21165920 has 24 divisors (see below), whose sum is σ = 50004864. Its totient is φ = 8466304.

The previous prime is 21165919. The next prime is 21165923. The reversal of 21165920 is 2956112.

It is a self number, because there is not a number n which added to its sum of digits gives 21165920.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21165923) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 65984 + ... + 66303.

It is an arithmetic number, because the mean of its divisors is an integer number (2083536).

Almost surely, 2^21165920 is an apocalyptic number.

21165920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21165920 is an abundant number, since it is smaller than the sum of its proper divisors (28838944).

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

21165920 is a wasteful number, since it uses less digits than its factorization.

21165920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 132302 (or 132294 counting only the distinct ones).

The product of its (nonzero) digits is 1080, while the sum is 26.

The square root of 21165920 is about 4600.6434332602. The cubic root of 21165920 is about 276.6171166565.

The spelling of 21165920 in words is "twenty-one million, one hundred sixty-five thousand, nine hundred twenty".