21086018 has 18 divisors (see below), whose sum is σ = 33775833. Its totient is φ = 9870880.

The previous prime is 21086017. The next prime is 21086027. The reversal of 21086018 is 81068012.

It can be written as a sum of positive squares in 2 ways, for example, as 19298449 + 1787569 = 4393^2 + 1337^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=3247.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21086011) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 110303 + ... + 110493.

Almost surely, 2^21086018 is an apocalyptic number.

21086018 is a deficient number, since it is larger than the sum of its proper divisors (12689815).

21086018 is an equidigital number, since it uses as much as digits as its factorization.

21086018 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 418 (or 210 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 26.

The square root of 21086018 is about 4591.9514370254. The cubic root of 21086018 is about 276.2685983534.

The spelling of 21086018 in words is "twenty-one million, eighty-six thousand, eighteen".