18665551 has 2 divisors, whose sum is σ = 18665552. Its totient is φ = 18665550.

The previous prime is 18665513. The next prime is 18665587. The reversal of 18665551 is 15556681.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 18665551 - 2⁹ = 18665039 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18665551.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18665651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9332775 + 9332776.

It is an arithmetic number, because the mean of its divisors is an integer number (9332776).

Almost surely, 2^18665551 is an apocalyptic number.

18665551 is a deficient number, since it is larger than the sum of its proper divisors (1).

18665551 is an equidigital number, since it uses as much as digits as its factorization.

18665551 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36000, while the sum is 37.

The square root of 18665551 is about 4320.3646836812. The cubic root of 18665551 is about 265.2651955384.

The spelling of 18665551 in words is "eighteen million, six hundred sixty-five thousand, five hundred fifty-one".