91257561 has 12 divisors (see below), whose sum is σ = 133486080. Its totient is φ = 60067800.

The previous prime is 91257559. The next prime is 91257563. The reversal of 91257561 is 16575219.

91257561 is a `hidden beast` number, since 91 + 2 + 5 + 7 + 561 = 666.

It is an interprime number because it is at equal distance from previous prime (91257559) and next prime (91257563).

It is not a de Polignac number, because 91257561 - 2¹ = 91257559 is a prime.

It is not an unprimeable number, because it can be changed into a prime (91257563) 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, 63465 + ... + 64886.

It is an arithmetic number, because the mean of its divisors is an integer number (11123840).

Almost surely, 2^91257561 is an apocalyptic number.

It is an amenable number.

91257561 is a deficient number, since it is larger than the sum of its proper divisors (42228519).

91257561 is a wasteful number, since it uses less digits than its factorization.

91257561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128436 (or 128433 counting only the distinct ones).

The product of its digits is 18900, while the sum is 36.

The square root of 91257561 is about 9552.8823399014. The cubic root of 91257561 is about 450.2181016829.

The spelling of 91257561 in words is "ninety-one million, two hundred fifty-seven thousand, five hundred sixty-one".