91000001 has 4 divisors (see below), whose sum is σ = 91154052. Its totient is φ = 90845952.

The previous prime is 90999989. The next prime is 91000009. The reversal of 91000001 is 10000019.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 77457601 + 13542400 = 8801^2 + 3680^2 .

It is a cyclic number.

It is not a de Polignac number, because 91000001 - 2¹⁴ = 90983617 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91000009) 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, 76136 + ... + 77321.

It is an arithmetic number, because the mean of its divisors is an integer number (22788513).

Almost surely, 2^91000001 is an apocalyptic number.

It is an amenable number.

91000001 is a deficient number, since it is larger than the sum of its proper divisors (154051).

91000001 is a wasteful number, since it uses less digits than its factorization.

91000001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 154050.

The product of its (nonzero) digits is 9, while the sum is 11.

The square root of 91000001 is about 9539.3920665837. The cubic root of 91000001 is about 449.7941461751.

It can be divided in two parts, 9 and 1000001, that multiplied together give a palindrome (9000009).

The spelling of 91000001 in words is "ninety-one million, one", and thus it is an aban number and an uban number.