18491399 has 2 divisors, whose sum is σ = 18491400. Its totient is φ = 18491398.

The previous prime is 18491381. The next prime is 18491413. The reversal of 18491399 is 99319481.

It is a strong prime.

It is an emirp because it is prime and its reverse (99319481) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18491399 - 2¹⁶ = 18425863 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18491339) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9245699 + 9245700.

It is an arithmetic number, because the mean of its divisors is an integer number (9245700).

Almost surely, 2^18491399 is an apocalyptic number.

18491399 is a deficient number, since it is larger than the sum of its proper divisors (1).

18491399 is an equidigital number, since it uses as much as digits as its factorization.

18491399 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 69984, while the sum is 44.

The square root of 18491399 is about 4300.1626713416. The cubic root of 18491399 is about 264.4376302426.

The spelling of 18491399 in words is "eighteen million, four hundred ninety-one thousand, three hundred ninety-nine".