21355920 has 80 divisors (see below), whose sum is σ = 73566720. Its totient is φ = 5694336.

The previous prime is 21355913. The next prime is 21355921. The reversal of 21355920 is 2955312.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21355921) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2784 + ... + 7103.

It is an arithmetic number, because the mean of its divisors is an integer number (919584).

Almost surely, 2^21355920 is an apocalyptic number.

21355920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21355920 is an abundant number, since it is smaller than the sum of its proper divisors (52210800).

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

21355920 is a wasteful number, since it uses less digits than its factorization.

21355920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9909 (or 9897 counting only the distinct ones).

The product of its (nonzero) digits is 2700, while the sum is 27.

The square root of 21355920 is about 4621.2465850677. The cubic root of 21355920 is about 277.4423547171.

The spelling of 21355920 in words is "twenty-one million, three hundred fifty-five thousand, nine hundred twenty".