991973999 has 2 divisors, whose sum is σ = 991974000. Its totient is φ = 991973998.

The previous prime is 991973993. The next prime is 991974001. The reversal of 991973999 is 999379199.

991973999 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 991973999 - 2¹² = 991969903 is a prime.

Together with 991974001, 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 (991973993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495986999 + 495987000.

It is an arithmetic number, because the mean of its divisors is an integer number (495987000).

Almost surely, 2^991973999 is an apocalyptic number.

991973999 is a deficient number, since it is larger than the sum of its proper divisors (1).

991973999 is an equidigital number, since it uses as much as digits as its factorization.

991973999 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 11160261, while the sum is 65.

The square root of 991973999 is about 31495.6187270547. The cubic root of 991973999 is about 997.3174768372.

The spelling of 991973999 in words is "nine hundred ninety-one million, nine hundred seventy-three thousand, nine hundred ninety-nine".