91998989 has 4 divisors (see below), whose sum is σ = 92029824. Its totient is φ = 91968156.

The previous prime is 91998961. The next prime is 91999009. The reversal of 91998989 is 98989919.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 91998989 - 2¹⁶ = 91933453 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91991989) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10397 + ... + 17090.

It is an arithmetic number, because the mean of its divisors is an integer number (23007456).

Almost surely, 2^91998989 is an apocalyptic number.

It is an amenable number.

91998989 is a deficient number, since it is larger than the sum of its proper divisors (30835).

91998989 is a wasteful number, since it uses less digits than its factorization.

91998989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30834.

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

The square root of 91998989 is about 9591.6103444625. The cubic root of 91998989 is about 451.4340899126.

The spelling of 91998989 in words is "ninety-one million, nine hundred ninety-eight thousand, nine hundred eighty-nine".