991397983 has 2 divisors, whose sum is σ = 991397984. Its totient is φ = 991397982.

The previous prime is 991397951. The next prime is 991397987. The reversal of 991397983 is 389793199.

It is a strong prime.

It is an emirp because it is prime and its reverse (389793199) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 991397983 - 2⁵ = 991397951 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991397987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495698991 + 495698992.

It is an arithmetic number, because the mean of its divisors is an integer number (495698992).

Almost surely, 2^991397983 is an apocalyptic number.

991397983 is a deficient number, since it is larger than the sum of its proper divisors (1).

991397983 is an equidigital number, since it uses as much as digits as its factorization.

991397983 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3306744, while the sum is 58.

The square root of 991397983 is about 31486.4730162017. The cubic root of 991397983 is about 997.1243998500.

The spelling of 991397983 in words is "nine hundred ninety-one million, three hundred ninety-seven thousand, nine hundred eighty-three".