91971840 has 144 divisors (see below), whose sum is σ = 301105728. Its totient is φ = 23912448.

The previous prime is 91971839. The next prime is 91971877. The reversal of 91971840 is 4817919.

It is a happy number.

It is a super-3 number, since 3×91971840³ (a number of 25 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 164842 + ... + 165398.

It is an arithmetic number, because the mean of its divisors is an integer number (2091012).

Almost surely, 2^91971840 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 91971840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (150552864).

91971840 is an abundant number, since it is smaller than the sum of its proper divisors (209133888).

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

91971840 is a wasteful number, since it uses less digits than its factorization.

91971840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 624 (or 610 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 39.

The square root of 91971840 is about 9590.1949928038. The cubic root of 91971840 is about 451.3896793163.

The spelling of 91971840 in words is "ninety-one million, nine hundred seventy-one thousand, eight hundred forty".