21881915 has 16 divisors (see below), whose sum is σ = 28809216. Its totient is φ = 15823200.

The previous prime is 21881903. The next prime is 21881917. The reversal of 21881915 is 51918812.

It is not a de Polignac number, because 21881915 - 2⁶ = 21881851 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21881917) 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, 9464 + ... + 11546.

It is an arithmetic number, because the mean of its divisors is an integer number (1800576).

Almost surely, 2^21881915 is an apocalyptic number.

21881915 is a deficient number, since it is larger than the sum of its proper divisors (6927301).

21881915 is a wasteful number, since it uses less digits than its factorization.

21881915 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2290.

The product of its digits is 5760, while the sum is 35.

The square root of 21881915 is about 4677.8109196503. The cubic root of 21881915 is about 279.7017018786.

The spelling of 21881915 in words is "twenty-one million, eight hundred eighty-one thousand, nine hundred fifteen".