18031681 has 2 divisors, whose sum is σ = 18031682. Its totient is φ = 18031680.

The previous prime is 18031633. The next prime is 18031687. The reversal of 18031681 is 18613081.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13808656 + 4223025 = 3716^2 + 2055^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18031681 is a prime.

It is a super-2 number, since 2×18031681² = 650283039371522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (18031687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9015840 + 9015841.

It is an arithmetic number, because the mean of its divisors is an integer number (9015841).

Almost surely, 2^18031681 is an apocalyptic number.

It is an amenable number.

18031681 is a deficient number, since it is larger than the sum of its proper divisors (1).

18031681 is an equidigital number, since it uses as much as digits as its factorization.

18031681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1152, while the sum is 28.

The square root of 18031681 is about 4246.3726873651. The cubic root of 18031681 is about 262.2278043182.

The spelling of 18031681 in words is "eighteen million, thirty-one thousand, six hundred eighty-one".