18640081 has 4 divisors (see below), whose sum is σ = 18668452. Its totient is φ = 18611712.

The previous prime is 18640079. The next prime is 18640087. The reversal of 18640081 is 18004681.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2310400 + 16329681 = 1520^2 + 4041^2 .

It is a cyclic number.

It is not a de Polignac number, because 18640081 - 2¹ = 18640079 is a prime.

It is a super-2 number, since 2×18640081² = 694905239373122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18640087) 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, 13176 + ... + 14521.

It is an arithmetic number, because the mean of its divisors is an integer number (4667113).

Almost surely, 2^18640081 is an apocalyptic number.

It is an amenable number.

18640081 is a deficient number, since it is larger than the sum of its proper divisors (28371).

18640081 is an equidigital number, since it uses as much as digits as its factorization.

18640081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28370.

The product of its (nonzero) digits is 1536, while the sum is 28.

The square root of 18640081 is about 4317.4160096057. The cubic root of 18640081 is about 265.1444851103.

The spelling of 18640081 in words is "eighteen million, six hundred forty thousand, eighty-one".