18390881 has 2 divisors, whose sum is σ = 18390882. Its totient is φ = 18390880.

The previous prime is 18390877. The next prime is 18390899. The reversal of 18390881 is 18809381.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17774656 + 616225 = 4216^2 + 785^2 .

It is a cyclic number.

It is not a de Polignac number, because 18390881 - 2² = 18390877 is a prime.

It is a super-2 number, since 2×18390881² = 676449007912322, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18390851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9195440 + 9195441.

It is an arithmetic number, because the mean of its divisors is an integer number (9195441).

Almost surely, 2^18390881 is an apocalyptic number.

It is an amenable number.

18390881 is a deficient number, since it is larger than the sum of its proper divisors (1).

18390881 is an equidigital number, since it uses as much as digits as its factorization.

18390881 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 13824, while the sum is 38.

The square root of 18390881 is about 4288.4590472570. The cubic root of 18390881 is about 263.9576043414.

The spelling of 18390881 in words is "eighteen million, three hundred ninety thousand, eight hundred eighty-one".