18500081 has 2 divisors, whose sum is σ = 18500082. Its totient is φ = 18500080.

The previous prime is 18500071. The next prime is 18500089. The reversal of 18500081 is 18000581.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17098225 + 1401856 = 4135^2 + 1184^2 .

It is a cyclic number.

It is not a de Polignac number, because 18500081 - 2⁶ = 18500017 is a prime.

It is a super-2 number, since 2×18500081² = 684505994013122, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18500089) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9250040 + 9250041.

It is an arithmetic number, because the mean of its divisors is an integer number (9250041).

Almost surely, 2^18500081 is an apocalyptic number.

It is an amenable number.

18500081 is a deficient number, since it is larger than the sum of its proper divisors (1).

18500081 is an equidigital number, since it uses as much as digits as its factorization.

18500081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 320, while the sum is 23.

The square root of 18500081 is about 4301.1720495697. The cubic root of 18500081 is about 264.4790096300.

Subtracting from 18500081 its reverse (18000581), we obtain a triangular number (499500 = T₉₉₉).

The spelling of 18500081 in words is "eighteen million, five hundred thousand, eighty-one".