99966991 has 2 divisors, whose sum is σ = 99966992. Its totient is φ = 99966990.

The previous prime is 99966989. The next prime is 99967001. The reversal of 99966991 is 19966999.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 99966991 - 2¹ = 99966989 is a prime.

Together with 99966989, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (99946991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 49983495 + 49983496.

It is an arithmetic number, because the mean of its divisors is an integer number (49983496).

Almost surely, 2^99966991 is an apocalyptic number.

99966991 is a deficient number, since it is larger than the sum of its proper divisors (1).

99966991 is an equidigital number, since it uses as much as digits as its factorization.

99966991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2125764, while the sum is 58.

The square root of 99966991 is about 9998.3494137783. The cubic root of 99966991 is about 464.1078063389.

The spelling of 99966991 in words is "ninety-nine million, nine hundred sixty-six thousand, nine hundred ninety-one".