91581840 has 240 divisors, whose sum is σ = 365059968. Its totient is φ = 20901888.

The previous prime is 91581829. The next prime is 91581877. The reversal of 91581840 is 4818519.

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 91581795 and 91581804.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 135744 + ... + 136416.

Almost surely, 2^91581840 is an apocalyptic number.

91581840 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 91581840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (182529984).

91581840 is an abundant number, since it is smaller than the sum of its proper divisors (273478128).

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

91581840 is a wasteful number, since it uses less digits than its factorization.

91581840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 708 (or 690 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 36.

The square root of 91581840 is about 9569.8401240564. The cubic root of 91581840 is about 450.7507468129.

The spelling of 91581840 in words is "ninety-one million, five hundred eighty-one thousand, eight hundred forty".