21151920 has 80 divisors (see below), whose sum is σ = 67709952. Its totient is φ = 5456640.

The previous prime is 21151919. The next prime is 21151937. The reversal of 21151920 is 2915112.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6019 + ... + 8861.

Almost surely, 2^21151920 is an apocalyptic number.

21151920 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 21151920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33854976).

21151920 is an abundant number, since it is smaller than the sum of its proper divisors (46558032).

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

21151920 is a wasteful number, since it uses less digits than its factorization.

21151920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2890 (or 2884 counting only the distinct ones).

The product of its (nonzero) digits is 180, while the sum is 21.

The square root of 21151920 is about 4599.1216552729. The cubic root of 21151920 is about 276.5561146025.

The spelling of 21151920 in words is "twenty-one million, one hundred fifty-one thousand, nine hundred twenty".