18328991 has 2 divisors, whose sum is σ = 18328992. Its totient is φ = 18328990.

The previous prime is 18328987. The next prime is 18328997. The reversal of 18328991 is 19982381.

It is a weak prime.

It is an emirp because it is prime and its reverse (19982381) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18328991 - 2² = 18328987 is a prime.

It is a super-2 number, since 2×18328991² = 671903822156162, which contains 22 as substring.

It is a Sophie Germain 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 (18328997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9164495 + 9164496.

It is an arithmetic number, because the mean of its divisors is an integer number (9164496).

Almost surely, 2^18328991 is an apocalyptic number.

18328991 is a deficient number, since it is larger than the sum of its proper divisors (1).

18328991 is an equidigital number, since it uses as much as digits as its factorization.

18328991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 31104, while the sum is 41.

The square root of 18328991 is about 4281.2370875718. The cubic root of 18328991 is about 263.6611767119.

The spelling of 18328991 in words is "eighteen million, three hundred twenty-eight thousand, nine hundred ninety-one".