18360721 has 2 divisors, whose sum is σ = 18360722. Its totient is φ = 18360720.

The previous prime is 18360659. The next prime is 18360733. The reversal of 18360721 is 12706381.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15249025 + 3111696 = 3905^2 + 1764^2 .

It is a cyclic number.

It is not a de Polignac number, because 18360721 - 2¹⁷ = 18229649 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18360721.

It is not a weakly prime, because it can be changed into another prime (18360781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9180360 + 9180361.

It is an arithmetic number, because the mean of its divisors is an integer number (9180361).

Almost surely, 2^18360721 is an apocalyptic number.

It is an amenable number.

18360721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18360721 is an equidigital number, since it uses as much as digits as its factorization.

18360721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 18360721 is about 4284.9411897948. The cubic root of 18360721 is about 263.8132335677.

The spelling of 18360721 in words is "eighteen million, three hundred sixty thousand, seven hundred twenty-one".