18625721 has 2 divisors, whose sum is σ = 18625722. Its totient is φ = 18625720.

The previous prime is 18625703. The next prime is 18625723. The reversal of 18625721 is 12752681.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9834496 + 8791225 = 3136^2 + 2965^2 .

It is a cyclic number.

It is not a de Polignac number, because 18625721 - 2⁶ = 18625657 is a prime.

Together with 18625723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18625723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9312860 + 9312861.

It is an arithmetic number, because the mean of its divisors is an integer number (9312861).

Almost surely, 2^18625721 is an apocalyptic number.

It is an amenable number.

18625721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18625721 is an equidigital number, since it uses as much as digits as its factorization.

18625721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6720, while the sum is 32.

The square root of 18625721 is about 4315.7526574168. The cubic root of 18625721 is about 265.0763800242.

The spelling of 18625721 in words is "eighteen million, six hundred twenty-five thousand, seven hundred twenty-one".