18312881 has 2 divisors, whose sum is σ = 18312882. Its totient is φ = 18312880.

The previous prime is 18312863. The next prime is 18312919. The reversal of 18312881 is 18821381.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10995856 + 7317025 = 3316^2 + 2705^2 .

It is a cyclic number.

It is not a de Polignac number, because 18312881 - 2¹⁰ = 18311857 is a prime.

It is a super-2 number, since 2×18312881² = 670723221040322, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (18312821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9156440 + 9156441.

It is an arithmetic number, because the mean of its divisors is an integer number (9156441).

Almost surely, 2^18312881 is an apocalyptic number.

It is an amenable number.

18312881 is a deficient number, since it is larger than the sum of its proper divisors (1).

18312881 is an equidigital number, since it uses as much as digits as its factorization.

18312881 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3072, while the sum is 32.

The square root of 18312881 is about 4279.3552084397. The cubic root of 18312881 is about 263.5839070172.

The spelling of 18312881 in words is "eighteen million, three hundred twelve thousand, eight hundred eighty-one".