91988813 has 4 divisors (see below), whose sum is σ = 105130080. Its totient is φ = 78847548.

The previous prime is 91988803. The next prime is 91988821. The reversal of 91988813 is 31888919.

It is a happy number.

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 91988813 - 2¹⁸ = 91726669 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 (91988803) 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, 6570623 + ... + 6570636.

It is an arithmetic number, because the mean of its divisors is an integer number (26282520).

Almost surely, 2^91988813 is an apocalyptic number.

It is an amenable number.

91988813 is a deficient number, since it is larger than the sum of its proper divisors (13141267).

91988813 is a wasteful number, since it uses less digits than its factorization.

91988813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13141266.

The product of its digits is 124416, while the sum is 47.

The square root of 91988813 is about 9591.0798662090. The cubic root of 91988813 is about 451.4174449373.

The spelling of 91988813 in words is "ninety-one million, nine hundred eighty-eight thousand, eight hundred thirteen".