91998731 has 8 divisors (see below), whose sum is σ = 103600128. Its totient is φ = 80937000.

The previous prime is 91998727. The next prime is 91998737. The reversal of 91998731 is 13789919.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 91998731 - 2² = 91998727 is a prime.

It is a super-3 number, since 3×91998731³ (a number of 25 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91998737) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 134555 + ... + 135236.

It is an arithmetic number, because the mean of its divisors is an integer number (12950016).

Almost surely, 2^91998731 is an apocalyptic number.

91998731 is a deficient number, since it is larger than the sum of its proper divisors (11601397).

91998731 is a wasteful number, since it uses less digits than its factorization.

91998731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 269833.

The product of its digits is 122472, while the sum is 47.

The square root of 91998731 is about 9591.5968951995. The cubic root of 91998731 is about 451.4336679148.

It can be divided in two parts, 91998 and 731, that added together give a palindrome (92729).

The spelling of 91998731 in words is "ninety-one million, nine hundred ninety-eight thousand, seven hundred thirty-one".