99891989 has 2 divisors, whose sum is σ = 99891990. Its totient is φ = 99891988.

The previous prime is 99891947. The next prime is 99891991. The reversal of 99891989 is 98919899.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 96687889 + 3204100 = 9833^2 + 1790^2 .

It is a cyclic number.

It is not a de Polignac number, because 99891989 - 2⁸ = 99891733 is a prime.

It is a super-2 number, since 2×99891989² = 19956818932752242, which contains 22 as substring.

Together with 99891991, 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 (99891919) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 49945994 + 49945995.

It is an arithmetic number, because the mean of its divisors is an integer number (49945995).

Almost surely, 2^99891989 is an apocalyptic number.

It is an amenable number.

99891989 is a deficient number, since it is larger than the sum of its proper divisors (1).

99891989 is an equidigital number, since it uses as much as digits as its factorization.

99891989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3779136, while the sum is 62.

The square root of 99891989 is about 9994.5979909149. The cubic root of 99891989 is about 463.9917089407.

The spelling of 99891989 in words is "ninety-nine million, eight hundred ninety-one thousand, nine hundred eighty-nine".