90991217 has 2 divisors, whose sum is σ = 90991218. Its totient is φ = 90991216.

The previous prime is 90991213. The next prime is 90991267. The reversal of 90991217 is 71219909.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 87590881 + 3400336 = 9359^2 + 1844^2 .

It is a cyclic number.

It is not a de Polignac number, because 90991217 - 2² = 90991213 is a prime.

It is a super-2 number, since 2×90991217² = 16558803142282178, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (90991213) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45495608 + 45495609.

It is an arithmetic number, because the mean of its divisors is an integer number (45495609).

Almost surely, 2^90991217 is an apocalyptic number.

It is an amenable number.

90991217 is a deficient number, since it is larger than the sum of its proper divisors (1).

90991217 is an equidigital number, since it uses as much as digits as its factorization.

90991217 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 38.

The square root of 90991217 is about 9538.9316487749. The cubic root of 90991217 is about 449.7796732122.

The spelling of 90991217 in words is "ninety million, nine hundred ninety-one thousand, two hundred seventeen".