91888721 has 8 divisors (see below), whose sum is σ = 94426464. Its totient is φ = 89369280.

The previous prime is 91888717. The next prime is 91888729. The reversal of 91888721 is 12788819.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 91888721 - 2² = 91888717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91888729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5930 + ... + 14796.

It is an arithmetic number, because the mean of its divisors is an integer number (11803308).

Almost surely, 2^91888721 is an apocalyptic number.

It is an amenable number.

91888721 is a deficient number, since it is larger than the sum of its proper divisors (2537743).

91888721 is a wasteful number, since it uses less digits than its factorization.

91888721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9151.

The product of its digits is 64512, while the sum is 44.

The square root of 91888721 is about 9585.8604725919. The cubic root of 91888721 is about 451.2536580914.

The spelling of 91888721 in words is "ninety-one million, eight hundred eighty-eight thousand, seven hundred twenty-one".