21901220 has 24 divisors (see below), whose sum is σ = 50174208. Its totient is φ = 7964000.

The previous prime is 21901211. The next prime is 21901247. The reversal of 21901220 is 2210912.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 49556 + ... + 49995.

It is an arithmetic number, because the mean of its divisors is an integer number (2090592).

Almost surely, 2^21901220 is an apocalyptic number.

21901220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21901220 is an abundant number, since it is smaller than the sum of its proper divisors (28272988).

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

21901220 is a wasteful number, since it uses less digits than its factorization.

21901220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 99571 (or 99569 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 17.

The square root of 21901220 is about 4679.8739299259. The cubic root of 21901220 is about 279.7839319488.

The spelling of 21901220 in words is "twenty-one million, nine hundred one thousand, two hundred twenty".