21911920 has 20 divisors (see below), whose sum is σ = 50945400. Its totient is φ = 8764736.

The previous prime is 21911909. The next prime is 21911957. The reversal of 21911920 is 2911912.

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

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, 136870 + ... + 137029.

It is an arithmetic number, because the mean of its divisors is an integer number (2547270).

Almost surely, 2^21911920 is an apocalyptic number.

21911920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21911920 is an abundant number, since it is smaller than the sum of its proper divisors (29033480).

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

21911920 is a wasteful number, since it uses less digits than its factorization.

21911920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 273912 (or 273906 counting only the distinct ones).

The product of its (nonzero) digits is 324, while the sum is 25.

The square root of 21911920 is about 4681.0169835197. The cubic root of 21911920 is about 279.8294880209.

The spelling of 21911920 in words is "twenty-one million, nine hundred eleven thousand, nine hundred twenty".