18917920 has 144 divisors (see below), whose sum is σ = 55157760. Its totient is φ = 6096384.

The previous prime is 18917917. The next prime is 18917959. The reversal of 18917920 is 2971981.

It is a self number, because there is not a number n which added to its sum of digits gives 18917920.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 148897 + ... + 149023.

It is an arithmetic number, because the mean of its divisors is an integer number (383040).

Almost surely, 2^18917920 is an apocalyptic number.

18917920 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18917920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27578880).

18917920 is an abundant number, since it is smaller than the sum of its proper divisors (36239840).

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

18917920 is a wasteful number, since it uses less digits than its factorization.

18917920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 175 (or 160 counting only the distinct ones).

The product of its (nonzero) digits is 9072, while the sum is 37.

The square root of 18917920 is about 4349.4735313599. The cubic root of 18917920 is about 266.4553603832.

The spelling of 18917920 in words is "eighteen million, nine hundred seventeen thousand, nine hundred twenty".