91421557 has 4 divisors (see below), whose sum is σ = 91652236. Its totient is φ = 91190880.

The previous prime is 91421537. The next prime is 91421581. The reversal of 91421557 is 75512419.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 62110161 + 29311396 = 7881^2 + 5414^2 .

It is a cyclic number.

It is not a de Polignac number, because 91421557 - 2¹¹ = 91419509 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91421537) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 114744 + ... + 115537.

It is an arithmetic number, because the mean of its divisors is an integer number (22913059).

Almost surely, 2^91421557 is an apocalyptic number.

It is an amenable number.

91421557 is a deficient number, since it is larger than the sum of its proper divisors (230679).

91421557 is a wasteful number, since it uses less digits than its factorization.

91421557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 230678.

The product of its digits is 12600, while the sum is 34.

The square root of 91421557 is about 9561.4620743901. The cubic root of 91421557 is about 450.4876310709.

The spelling of 91421557 in words is "ninety-one million, four hundred twenty-one thousand, five hundred fifty-seven".