91723721 has 8 divisors (see below), whose sum is σ = 97203744. Its totient is φ = 86253120.

The previous prime is 91723651. The next prime is 91723729. The reversal of 91723721 is 12732719.

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 91723721 - 2¹⁴ = 91707337 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91723729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 32846 + ... + 35528.

It is an arithmetic number, because the mean of its divisors is an integer number (12150468).

Almost surely, 2^91723721 is an apocalyptic number.

It is an amenable number.

91723721 is a deficient number, since it is larger than the sum of its proper divisors (5480023).

91723721 is a wasteful number, since it uses less digits than its factorization.

91723721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4711.

The product of its digits is 5292, while the sum is 32.

The square root of 91723721 is about 9577.2501794617. The cubic root of 91723721 is about 450.9833983561.

The spelling of 91723721 in words is "ninety-one million, seven hundred twenty-three thousand, seven hundred twenty-one".