21986915 has 4 divisors (see below), whose sum is σ = 26384304. Its totient is φ = 17589528.

The previous prime is 21986903. The next prime is 21986953. The reversal of 21986915 is 51968912.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21986915 - 2⁶ = 21986851 is a prime.

It is a Duffinian number.

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, 2198687 + ... + 2198696.

It is an arithmetic number, because the mean of its divisors is an integer number (6596076).

Almost surely, 2^21986915 is an apocalyptic number.

21986915 is a deficient number, since it is larger than the sum of its proper divisors (4397389).

21986915 is an equidigital number, since it uses as much as digits as its factorization.

21986915 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4397388.

The product of its digits is 38880, while the sum is 41.

The square root of 21986915 is about 4689.0206866680. The cubic root of 21986915 is about 280.1483694957.

The spelling of 21986915 in words is "twenty-one million, nine hundred eighty-six thousand, nine hundred fifteen".