91001920 has 56 divisors (see below), whose sum is σ = 218770200. Its totient is φ = 36052992.

The previous prime is 91001903. The next prime is 91001927. The reversal of 91001920 is 2910019.

It can be written as a sum of positive squares in 4 ways, for example, as 14684224 + 76317696 = 3832^2 + 8736^2 .

It is a junction number, because it is equal to n+sod(n) for n = 91001891 and 91001900.

It is not an unprimeable number, because it can be changed into a prime (91001927) 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, 33576 + ... + 36184.

Almost surely, 2^91001920 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 91001920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (109385100).

91001920 is an abundant number, since it is smaller than the sum of its proper divisors (127768280).

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

91001920 is a wasteful number, since it uses less digits than its factorization.

91001920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2735 (or 2725 counting only the distinct ones).

The product of its (nonzero) digits is 162, while the sum is 22.

The square root of 91001920 is about 9539.4926489830. The cubic root of 91001920 is about 449.7973078927.

Adding to 91001920 its reverse (2910019), we get a palindrome (93911939).

The spelling of 91001920 in words is "ninety-one million, one thousand, nine hundred twenty".