18918931 has 2 divisors, whose sum is σ = 18918932. Its totient is φ = 18918930.

The previous prime is 18918923. The next prime is 18918947. The reversal of 18918931 is 13981981.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 18918931 - 2³ = 18918923 is a prime.

It is a super-2 number, since 2×18918931² = 715851900365522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (18918961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9459465 + 9459466.

It is an arithmetic number, because the mean of its divisors is an integer number (9459466).

Almost surely, 2^18918931 is an apocalyptic number.

18918931 is a deficient number, since it is larger than the sum of its proper divisors (1).

18918931 is an equidigital number, since it uses as much as digits as its factorization.

18918931 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15552, while the sum is 40.

The square root of 18918931 is about 4349.5897507696. The cubic root of 18918931 is about 266.4601068805.

The spelling of 18918931 in words is "eighteen million, nine hundred eighteen thousand, nine hundred thirty-one".