91997640 has 256 divisors, whose sum is σ = 359884800. Its totient is φ = 20466432.

The previous prime is 91997629. The next prime is 91997669. The reversal of 91997640 is 4679919.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 324939 + ... + 325221.

It is an arithmetic number, because the mean of its divisors is an integer number (1405800).

Almost surely, 2^91997640 is an apocalyptic number.

91997640 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 91997640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (179942400).

91997640 is an abundant number, since it is smaller than the sum of its proper divisors (267887160).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

91997640 is a wasteful number, since it uses less digits than its factorization.

91997640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 353 (or 343 counting only the distinct ones).

The product of its (nonzero) digits is 122472, while the sum is 45.

The square root of 91997640 is about 9591.5400223322. The cubic root of 91997640 is about 451.4318834117.

The spelling of 91997640 in words is "ninety-one million, nine hundred ninety-seven thousand, six hundred forty".