90091171921 has 2 divisors, whose sum is σ = 90091171922. Its totient is φ = 90091171920.

The previous prime is 90091171909. The next prime is 90091171931. The reversal of 90091171921 is 12917119009.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 82276611921 + 7814560000 = 286839^2 + 88400^2 .

It is a cyclic number.

It is not a de Polignac number, because 90091171921 - 2⁵ = 90091171889 is a prime.

It is not a weakly prime, because it can be changed into another prime (90091171931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45045585960 + 45045585961.

It is an arithmetic number, because the mean of its divisors is an integer number (45045585961).

Almost surely, 2^90091171921 is an apocalyptic number.

It is an amenable number.

90091171921 is a deficient number, since it is larger than the sum of its proper divisors (1).

90091171921 is an equidigital number, since it uses as much as digits as its factorization.

90091171921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10206, while the sum is 40.

The spelling of 90091171921 in words is "ninety billion, ninety-one million, one hundred seventy-one thousand, nine hundred twenty-one".