91555661 has 4 divisors (see below), whose sum is σ = 96374400. Its totient is φ = 86736924.

The previous prime is 91555657. The next prime is 91555687. The reversal of 91555661 is 16655519.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 16655519 = 23 ⋅724153.

It is a cyclic number.

It is not a de Polignac number, because 91555661 - 2² = 91555657 is a prime.

It is a super-2 number, since 2×91555661² = 16764878122293842, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91555691) 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, 2409341 + ... + 2409378.

It is an arithmetic number, because the mean of its divisors is an integer number (24093600).

Almost surely, 2^91555661 is an apocalyptic number.

It is an amenable number.

91555661 is a deficient number, since it is larger than the sum of its proper divisors (4818739).

91555661 is a wasteful number, since it uses less digits than its factorization.

91555661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4818738.

The product of its digits is 40500, while the sum is 38.

The square root of 91555661 is about 9568.4722396002. The cubic root of 91555661 is about 450.7077931430.

The spelling of 91555661 in words is "ninety-one million, five hundred fifty-five thousand, six hundred sixty-one".