18317991 has 4 divisors (see below), whose sum is σ = 24423992. Its totient is φ = 12211992.

The previous prime is 18317989. The next prime is 18318007. The reversal of 18317991 is 19971381.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 18317991 - 2¹ = 18317989 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18317941) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3052996 + ... + 3053001.

It is an arithmetic number, because the mean of its divisors is an integer number (6105998).

Almost surely, 2^18317991 is an apocalyptic number.

18317991 is a deficient number, since it is larger than the sum of its proper divisors (6106001).

18317991 is an equidigital number, since it uses as much as digits as its factorization.

18317991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6106000.

The product of its digits is 13608, while the sum is 39.

The square root of 18317991 is about 4279.9522193595. The cubic root of 18317991 is about 263.6084214287.

The spelling of 18317991 in words is "eighteen million, three hundred seventeen thousand, nine hundred ninety-one".