91721397 has 8 divisors (see below), whose sum is σ = 123482944. Its totient is φ = 60553728.

The previous prime is 91721359. The next prime is 91721407. The reversal of 91721397 is 79312719.

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

It is not a de Polignac number, because 91721397 - 2¹¹ = 91719349 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 (91721327) 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, 148108 + ... + 148725.

It is an arithmetic number, because the mean of its divisors is an integer number (15435368).

Almost surely, 2^91721397 is an apocalyptic number.

It is an amenable number.

91721397 is a deficient number, since it is larger than the sum of its proper divisors (31761547).

91721397 is a wasteful number, since it uses less digits than its factorization.

91721397 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 296939.

The product of its digits is 23814, while the sum is 39.

The square root of 91721397 is about 9577.1288495039. The cubic root of 91721397 is about 450.9795894749.

The spelling of 91721397 in words is "ninety-one million, seven hundred twenty-one thousand, three hundred ninety-seven".