391099987 has 2 divisors, whose sum is σ = 391099988. Its totient is φ = 391099986.

The previous prime is 391099949. The next prime is 391099993. The reversal of 391099987 is 789990193.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 391099987 - 2²³ = 382711379 is a prime.

It is not a weakly prime, because it can be changed into another prime (391099927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 195549993 + 195549994.

It is an arithmetic number, because the mean of its divisors is an integer number (195549994).

Almost surely, 2^391099987 is an apocalyptic number.

391099987 is a deficient number, since it is larger than the sum of its proper divisors (1).

391099987 is an equidigital number, since it uses as much as digits as its factorization.

391099987 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1102248, while the sum is 55.

The square root of 391099987 is about 19776.2480516401. The cubic root of 391099987 is about 731.3006068953.

The spelling of 391099987 in words is "three hundred ninety-one million, ninety-nine thousand, nine hundred eighty-seven".