91221217 has 2 divisors, whose sum is σ = 91221218. Its totient is φ = 91221216.

The previous prime is 91221203. The next prime is 91221307. The reversal of 91221217 is 71212219.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 84713616 + 6507601 = 9204^2 + 2551^2 .

It is a cyclic number.

It is not a de Polignac number, because 91221217 - 2⁷ = 91221089 is a prime.

It is a super-2 number, since 2×91221217² = 16642620861922178, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 91221191 and 91221200.

It is not a weakly prime, because it can be changed into another prime (91221517) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45610608 + 45610609.

It is an arithmetic number, because the mean of its divisors is an integer number (45610609).

Almost surely, 2^91221217 is an apocalyptic number.

It is an amenable number.

91221217 is a deficient number, since it is larger than the sum of its proper divisors (1).

91221217 is an equidigital number, since it uses as much as digits as its factorization.

91221217 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 504, while the sum is 25.

The square root of 91221217 is about 9550.9798973718. The cubic root of 91221217 is about 450.1583261816.

The spelling of 91221217 in words is "ninety-one million, two hundred twenty-one thousand, two hundred seventeen".