91987979 has 2 divisors, whose sum is σ = 91987980. Its totient is φ = 91987978.

The previous prime is 91987963. The next prime is 91987991. The reversal of 91987979 is 97978919.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 91987979 - 2⁴ = 91987963 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (91987919) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45993989 + 45993990.

It is an arithmetic number, because the mean of its divisors is an integer number (45993990).

Almost surely, 2^91987979 is an apocalyptic number.

91987979 is a deficient number, since it is larger than the sum of its proper divisors (1).

91987979 is an equidigital number, since it uses as much as digits as its factorization.

91987979 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2571912, while the sum is 59.

The square root of 91987979 is about 9591.0363882117. The cubic root of 91987979 is about 451.4160807016.

The spelling of 91987979 in words is "ninety-one million, nine hundred eighty-seven thousand, nine hundred seventy-nine".