91720001 has 4 divisors (see below), whose sum is σ = 93011904. Its totient is φ = 90428100.

The previous prime is 91719977. The next prime is 91720009. The reversal of 91720001 is 10002719.

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: 10002719 = 61 ⋅163979.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-91720001 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91720009) 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 3 ways as a sum of consecutive naturals, for example, 645845 + ... + 645986.

It is an arithmetic number, because the mean of its divisors is an integer number (23252976).

Almost surely, 2^91720001 is an apocalyptic number.

It is an amenable number.

91720001 is a deficient number, since it is larger than the sum of its proper divisors (1291903).

91720001 is a wasteful number, since it uses less digits than its factorization.

91720001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1291902.

The product of its (nonzero) digits is 126, while the sum is 20.

The square root of 91720001 is about 9577.0559672584. The cubic root of 91720001 is about 450.9773014930.

The spelling of 91720001 in words is "ninety-one million, seven hundred twenty thousand, one".