91169821 has 2 divisors, whose sum is σ = 91169822. Its totient is φ = 91169820.

The previous prime is 91169803. The next prime is 91169831. The reversal of 91169821 is 12896119.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 84088900 + 7080921 = 9170^2 + 2661^2 .

It is a cyclic number.

It is not a de Polignac number, because 91169821 - 2⁷ = 91169693 is a prime.

It is a super-2 number, since 2×91169821² = 16623872522344082, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91169831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45584910 + 45584911.

It is an arithmetic number, because the mean of its divisors is an integer number (45584911).

Almost surely, 2^91169821 is an apocalyptic number.

It is an amenable number.

91169821 is a deficient number, since it is larger than the sum of its proper divisors (1).

91169821 is an equidigital number, since it uses as much as digits as its factorization.

91169821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7776, while the sum is 37.

The square root of 91169821 is about 9548.2889043011. The cubic root of 91169821 is about 450.0737673307.

The spelling of 91169821 in words is "ninety-one million, one hundred sixty-nine thousand, eight hundred twenty-one".