18645681 has 4 divisors (see below), whose sum is σ = 24860912. Its totient is φ = 12430452.

The previous prime is 18645673. The next prime is 18645689. The reversal of 18645681 is 18654681.

18645681 is nontrivially palindromic in base 11.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 18654681 = 3 ⋅6218227.

It is an interprime number because it is at equal distance from previous prime (18645673) and next prime (18645689).

It is not a de Polignac number, because 18645681 - 2³ = 18645673 is a prime.

It is a super-2 number, since 2×18645681² = 695322839907522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18645689) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3107611 + ... + 3107616.

It is an arithmetic number, because the mean of its divisors is an integer number (6215228).

Almost surely, 2^18645681 is an apocalyptic number.

It is an amenable number.

18645681 is a deficient number, since it is larger than the sum of its proper divisors (6215231).

18645681 is an equidigital number, since it uses as much as digits as its factorization.

18645681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6215230.

The product of its digits is 46080, while the sum is 39.

The square root of 18645681 is about 4318.0644969708. The cubic root of 18645681 is about 265.1710347168.

The spelling of 18645681 in words is "eighteen million, six hundred forty-five thousand, six hundred eighty-one".