18997986 has 72 divisors (see below), whose sum is σ = 46908720. Its totient is φ = 5113584.

The previous prime is 18997973. The next prime is 18997991. The reversal of 18997986 is 68979981.

It is a Harshad number since it is a multiple of its sum of digits (57).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 106045 + ... + 106223.

It is an arithmetic number, because the mean of its divisors is an integer number (651510).

Almost surely, 2^18997986 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18997986, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23454360).

18997986 is an abundant number, since it is smaller than the sum of its proper divisors (27910734).

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

18997986 is a wasteful number, since it uses less digits than its factorization.

18997986 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 236 (or 210 counting only the distinct ones).

The product of its digits is 1959552, while the sum is 57.

The square root of 18997986 is about 4358.6679157743. The cubic root of 18997986 is about 266.8307361865.

The spelling of 18997986 in words is "eighteen million, nine hundred ninety-seven thousand, nine hundred eighty-six".