20815818 has 16 divisors (see below), whose sum is σ = 42974976. Its totient is φ = 6714720.

The previous prime is 20815807. The next prime is 20815831. The reversal of 20815818 is 81851802.

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, 55771 + ... + 56142.

It is an arithmetic number, because the mean of its divisors is an integer number (2685936).

Almost surely, 2^20815818 is an apocalyptic number.

20815818 is an abundant number, since it is smaller than the sum of its proper divisors (22159158).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20815818 is a wasteful number, since it uses less digits than its factorization.

20815818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 111949.

The product of its (nonzero) digits is 5120, while the sum is 33.

The square root of 20815818 is about 4562.4355337911. The cubic root of 20815818 is about 275.0834699788.

The spelling of 20815818 in words is "twenty million, eight hundred fifteen thousand, eight hundred eighteen".