991939999 has 2 divisors, whose sum is σ = 991940000. Its totient is φ = 991939998.

The previous prime is 991939981. The next prime is 991940009. The reversal of 991939999 is 999939199.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 991939999 - 2¹⁷ = 991808927 is a prime.

It is a super-2 number, since 2×991939999² = 1967889923232240002, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991939939) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495969999 + 495970000.

It is an arithmetic number, because the mean of its divisors is an integer number (495970000).

Almost surely, 2^991939999 is an apocalyptic number.

991939999 is a deficient number, since it is larger than the sum of its proper divisors (1).

991939999 is an equidigital number, since it uses as much as digits as its factorization.

991939999 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 14348907, while the sum is 67.

The square root of 991939999 is about 31495.0789648161. The cubic root of 991939999 is about 997.3060823243.

The spelling of 991939999 in words is "nine hundred ninety-one million, nine hundred thirty-nine thousand, nine hundred ninety-nine".