21378986 has 8 divisors (see below), whose sum is σ = 32088420. Its totient is φ = 10682848.

The previous prime is 21378953. The next prime is 21378991. The reversal of 21378986 is 68987312.

It can be written as a sum of positive squares in 2 ways, for example, as 17098225 + 4280761 = 4135^2 + 2069^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21378986² = 914122084776392, which contains 22 as substring.

It is a Curzon number.

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 3 ways as a sum of consecutive naturals, for example, 3500 + ... + 7416.

Almost surely, 2^21378986 is an apocalyptic number.

21378986 is a deficient number, since it is larger than the sum of its proper divisors (10709434).

21378986 is a wasteful number, since it uses less digits than its factorization.

21378986 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6648.

The product of its digits is 145152, while the sum is 44.

The square root of 21378986 is about 4623.7415585216. The cubic root of 21378986 is about 277.5422049813.

The spelling of 21378986 in words is "twenty-one million, three hundred seventy-eight thousand, nine hundred eighty-six".