90391991 has 2 divisors, whose sum is σ = 90391992. Its totient is φ = 90391990.

The previous prime is 90391979. The next prime is 90391993. The reversal of 90391991 is 19919309.

It is a strong prime.

It is an emirp because it is prime and its reverse (19919309) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 90391991 - 2¹⁰ = 90390967 is a prime.

Together with 90391993, 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 (90391993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45195995 + 45195996.

It is an arithmetic number, because the mean of its divisors is an integer number (45195996).

Almost surely, 2^90391991 is an apocalyptic number.

90391991 is a deficient number, since it is larger than the sum of its proper divisors (1).

90391991 is an equidigital number, since it uses as much as digits as its factorization.

90391991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 19683, while the sum is 41.

The square root of 90391991 is about 9507.4702734218. The cubic root of 90391991 is about 448.7901509945.

The spelling of 90391991 in words is "ninety million, three hundred ninety-one thousand, nine hundred ninety-one".