91215840 has 96 divisors (see below), whose sum is σ = 288731520. Its totient is φ = 24205824.

The previous prime is 91215811. The next prime is 91215847. The reversal of 91215840 is 4851219.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 91215798 and 91215807.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91215847) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 147051 + ... + 147669.

It is an arithmetic number, because the mean of its divisors is an integer number (3007620).

Almost surely, 2^91215840 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 91215840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (144365760).

91215840 is an abundant number, since it is smaller than the sum of its proper divisors (197515680).

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

91215840 is a wasteful number, since it uses less digits than its factorization.

91215840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 944 (or 936 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 30.

The square root of 91215840 is about 9550.6984037818. The cubic root of 91215840 is about 450.1494812040.

The spelling of 91215840 in words is "ninety-one million, two hundred fifteen thousand, eight hundred forty".