90917821 has 2 divisors, whose sum is σ = 90917822. Its totient is φ = 90917820.

The previous prime is 90917807. The next prime is 90917833. The reversal of 90917821 is 12871909.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 78765625 + 12152196 = 8875^2 + 3486^2 .

It is a cyclic number.

It is not a de Polignac number, because 90917821 - 2¹⁹ = 90393533 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (90917891) 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, 45458910 + 45458911.

It is an arithmetic number, because the mean of its divisors is an integer number (45458911).

Almost surely, 2^90917821 is an apocalyptic number.

It is an amenable number.

90917821 is a deficient number, since it is larger than the sum of its proper divisors (1).

90917821 is an equidigital number, since it uses as much as digits as its factorization.

90917821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9072, while the sum is 37.

The square root of 90917821 is about 9535.0836912950. The cubic root of 90917821 is about 449.6587058262.

The spelling of 90917821 in words is "ninety million, nine hundred seventeen thousand, eight hundred twenty-one".