20981918 has 8 divisors (see below), whose sum is σ = 31492800. Its totient is φ = 10484320.

The previous prime is 20981899. The next prime is 20981929. The reversal of 20981918 is 81918902.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3158 + ... + 7206.

It is an arithmetic number, because the mean of its divisors is an integer number (3936600).

Almost surely, 2^20981918 is an apocalyptic number.

20981918 is a deficient number, since it is larger than the sum of its proper divisors (10510882).

20981918 is a wasteful number, since it uses less digits than its factorization.

20981918 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6642.

The product of its (nonzero) digits is 10368, while the sum is 38.

The square root of 20981918 is about 4580.6023621354. The cubic root of 20981918 is about 275.8132093966.

The spelling of 20981918 in words is "twenty million, nine hundred eighty-one thousand, nine hundred eighteen".