18440813 has 2 divisors, whose sum is σ = 18440814. Its totient is φ = 18440812.

The previous prime is 18440791. The next prime is 18440831. The reversal of 18440813 is 31804481.

Together with next prime (18440831) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18130564 + 310249 = 4258^2 + 557^2 .

It is a cyclic number.

It is not a de Polignac number, because 18440813 - 2⁸ = 18440557 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18440833) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9220406 + 9220407.

It is an arithmetic number, because the mean of its divisors is an integer number (9220407).

Almost surely, 2^18440813 is an apocalyptic number.

It is an amenable number.

18440813 is a deficient number, since it is larger than the sum of its proper divisors (1).

18440813 is an equidigital number, since it uses as much as digits as its factorization.

18440813 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3072, while the sum is 29.

The square root of 18440813 is about 4294.2767726359. The cubic root of 18440813 is about 264.1962737313.

The spelling of 18440813 in words is "eighteen million, four hundred forty thousand, eight hundred thirteen".