999634991 has 2 divisors, whose sum is σ = 999634992. Its totient is φ = 999634990.

The previous prime is 999634919. The next prime is 999635009. The reversal of 999634991 is 199436999.

Together with previous prime (999634919) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-999634991 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 999634991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (999634591) 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, 499817495 + 499817496.

It is an arithmetic number, because the mean of its divisors is an integer number (499817496).

Almost surely, 2^999634991 is an apocalyptic number.

999634991 is a deficient number, since it is larger than the sum of its proper divisors (1).

999634991 is an equidigital number, since it uses as much as digits as its factorization.

999634991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4251528, while the sum is 59.

The square root of 999634991 is about 31617.0047759113. The cubic root of 999634991 is about 999.8783155268.

The spelling of 999634991 in words is "nine hundred ninety-nine million, six hundred thirty-four thousand, nine hundred ninety-one".