18507681 has 6 divisors (see below), whose sum is σ = 26733330. Its totient is φ = 12338448.

The previous prime is 18507661. The next prime is 18507701. The reversal of 18507681 is 18670581.

It is an interprime number because it is at equal distance from previous prime (18507661) and next prime (18507701).

It can be written as a sum of positive squares in only one way, i.e., 15563025 + 2944656 = 3945^2 + 1716^2 .

It is not a de Polignac number, because 18507681 - 2⁷ = 18507553 is a prime.

It is a super-2 number, since 2×18507681² = 685068511995522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (18507661) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1028196 + ... + 1028213.

It is an arithmetic number, because the mean of its divisors is an integer number (4455555).

Almost surely, 2^18507681 is an apocalyptic number.

It is an amenable number.

18507681 is a deficient number, since it is larger than the sum of its proper divisors (8225649).

18507681 is a wasteful number, since it uses less digits than its factorization.

18507681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2056415 (or 2056412 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 36.

The square root of 18507681 is about 4302.0554389733. The cubic root of 18507681 is about 264.5152214586.

The spelling of 18507681 in words is "eighteen million, five hundred seven thousand, six hundred eighty-one".