91001009 has 4 divisors (see below), whose sum is σ = 99273840. Its totient is φ = 82728180.

The previous prime is 91000999. The next prime is 91001059. The reversal of 91001009 is 90010019.

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.

It is a cyclic number.

It is not a de Polignac number, because 91001009 - 2²⁰ = 89952433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91001059) 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, 4136399 + ... + 4136420.

It is an arithmetic number, because the mean of its divisors is an integer number (24818460).

Almost surely, 2^91001009 is an apocalyptic number.

It is an amenable number.

91001009 is a deficient number, since it is larger than the sum of its proper divisors (8272831).

91001009 is a wasteful number, since it uses less digits than its factorization.

91001009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8272830.

The product of its (nonzero) digits is 81, while the sum is 20.

The square root of 91001009 is about 9539.4448999929. Note that the first 3 decimals coincide. The cubic root of 91001009 is about 449.7958069474.

The spelling of 91001009 in words is "ninety-one million, one thousand, nine".