21915440 has 20 divisors (see below), whose sum is σ = 50953584. Its totient is φ = 8766144.

The previous prime is 21915437. The next prime is 21915451. The reversal of 21915440 is 4451912.

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

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, 136892 + ... + 137051.

Almost surely, 2^21915440 is an apocalyptic number.

21915440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21915440 is an abundant number, since it is smaller than the sum of its proper divisors (29038144).

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

21915440 is a wasteful number, since it uses less digits than its factorization.

21915440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 273956 (or 273950 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 21915440 is about 4681.3929550936. The cubic root of 21915440 is about 279.8444714494.

The spelling of 21915440 in words is "twenty-one million, nine hundred fifteen thousand, four hundred forty".