18099721 has 2 divisors, whose sum is σ = 18099722. Its totient is φ = 18099720.

The previous prime is 18099671. The next prime is 18099743. The reversal of 18099721 is 12799081.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17943696 + 156025 = 4236^2 + 395^2 .

It is a cyclic number.

It is not a de Polignac number, because 18099721 - 2⁷ = 18099593 is a prime.

It is not a weakly prime, because it can be changed into another prime (18099751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9049860 + 9049861.

It is an arithmetic number, because the mean of its divisors is an integer number (9049861).

Almost surely, 2^18099721 is an apocalyptic number.

It is an amenable number.

18099721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18099721 is an equidigital number, since it uses as much as digits as its factorization.

18099721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9072, while the sum is 37.

The square root of 18099721 is about 4254.3766876007. The cubic root of 18099721 is about 262.5572168549.

The spelling of 18099721 in words is "eighteen million, ninety-nine thousand, seven hundred twenty-one".