18416581 has 2 divisors, whose sum is σ = 18416582. Its totient is φ = 18416580.

The previous prime is 18416579. The next prime is 18416597. The reversal of 18416581 is 18561481.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13616100 + 4800481 = 3690^2 + 2191^2 .

It is a cyclic number.

It is not a de Polignac number, because 18416581 - 2¹ = 18416579 is a prime.

It is a super-2 number, since 2×18416581² = 678340911459122, which contains 22 as substring.

Together with 18416579, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18416501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9208290 + 9208291.

It is an arithmetic number, because the mean of its divisors is an integer number (9208291).

Almost surely, 2^18416581 is an apocalyptic number.

It is an amenable number.

18416581 is a deficient number, since it is larger than the sum of its proper divisors (1).

18416581 is an equidigital number, since it uses as much as digits as its factorization.

18416581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7680, while the sum is 34.

The square root of 18416581 is about 4291.4544154634. The cubic root of 18416581 is about 264.0805013532.

The spelling of 18416581 in words is "eighteen million, four hundred sixteen thousand, five hundred eighty-one".