21545920 has 56 divisors (see below), whose sum is σ = 55979568. Its totient is φ = 7833600.

The previous prime is 21545911. The next prime is 21545957. The reversal of 21545920 is 2954512.

It is a congruent number.

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, 460 + ... + 6580.

Almost surely, 2^21545920 is an apocalyptic number.

21545920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21545920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27989784).

21545920 is an abundant number, since it is smaller than the sum of its proper divisors (34433648).

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

21545920 is a wasteful number, since it uses less digits than its factorization.

21545920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6149 (or 6139 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 28.

The square root of 21545920 is about 4641.7582875458. The cubic root of 21545920 is about 278.2627125104.

The spelling of 21545920 in words is "twenty-one million, five hundred forty-five thousand, nine hundred twenty".