18607991 has 2 divisors, whose sum is σ = 18607992. Its totient is φ = 18607990.

The previous prime is 18607987. The next prime is 18607993. The reversal of 18607991 is 19970681.

It is a happy number.

It is a strong prime.

It is an emirp because it is prime and its reverse (19970681) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18607991 - 2² = 18607987 is a prime.

Together with 18607993, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18607993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9303995 + 9303996.

It is an arithmetic number, because the mean of its divisors is an integer number (9303996).

Almost surely, 2^18607991 is an apocalyptic number.

18607991 is a deficient number, since it is larger than the sum of its proper divisors (1).

18607991 is an equidigital number, since it uses as much as digits as its factorization.

18607991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 27216, while the sum is 41.

The square root of 18607991 is about 4313.6980654654. The cubic root of 18607991 is about 264.9922437507.

The spelling of 18607991 in words is "eighteen million, six hundred seven thousand, nine hundred ninety-one".