21286018 has 16 divisors (see below), whose sum is σ = 35118720. Its totient is φ = 9614736.

The previous prime is 21286009. The next prime is 21286033. The reversal of 21286018 is 81068212.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7488 + ... + 9931.

It is an arithmetic number, because the mean of its divisors is an integer number (2194920).

Almost surely, 2^21286018 is an apocalyptic number.

21286018 is a deficient number, since it is larger than the sum of its proper divisors (13832702).

21286018 is a wasteful number, since it uses less digits than its factorization.

21286018 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17481.

The product of its (nonzero) digits is 1536, while the sum is 28.

The square root of 21286018 is about 4613.6772752328. The cubic root of 21286018 is about 277.1393165918.

It can be divided in two parts, 212860 and 18, that added together give a triangular number (212878 = T₆₅₂).

The spelling of 21286018 in words is "twenty-one million, two hundred eighty-six thousand, eighteen".