91288561 has 12 divisors (see below), whose sum is σ = 112973952. Its totient is φ = 72227376.

The previous prime is 91288537. The next prime is 91288579. The reversal of 91288561 is 16588219.

It is not a de Polignac number, because 91288561 - 2⁹ = 91288049 is a prime.

It is not an unprimeable number, because it can be changed into a prime (91288501) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 37401 + ... + 39766.

It is an arithmetic number, because the mean of its divisors is an integer number (9414496).

Almost surely, 2^91288561 is an apocalyptic number.

91288561 is a gapful number since it is divisible by the number (91) formed by its first and last digit.

It is an amenable number.

91288561 is a deficient number, since it is larger than the sum of its proper divisors (21685391).

91288561 is a wasteful number, since it uses less digits than its factorization.

91288561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77200 (or 77187 counting only the distinct ones).

The product of its digits is 34560, while the sum is 40.

The square root of 91288561 is about 9554.5047490699. The cubic root of 91288561 is about 450.2690752897.

It can be divided in two parts, 9128 and 8561, that added together give a square (17689 = 133²).

The spelling of 91288561 in words is "ninety-one million, two hundred eighty-eight thousand, five hundred sixty-one".