921921817 has 2 divisors, whose sum is σ = 921921818. Its totient is φ = 921921816.

The previous prime is 921921799. The next prime is 921921823. The reversal of 921921817 is 718129129.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 912704521 + 9217296 = 30211^2 + 3036^2 .

It is a cyclic number.

It is not a de Polignac number, because 921921817 - 2²³ = 913533209 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 921921817.

It is not a weakly prime, because it can be changed into another prime (921921877) 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, 460960908 + 460960909.

It is an arithmetic number, because the mean of its divisors is an integer number (460960909).

Almost surely, 2^921921817 is an apocalyptic number.

It is an amenable number.

921921817 is a deficient number, since it is larger than the sum of its proper divisors (1).

921921817 is an equidigital number, since it uses as much as digits as its factorization.

921921817 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18144, while the sum is 40.

The square root of 921921817 is about 30363.1654640948. The cubic root of 921921817 is about 973.2655790262.

The spelling of 921921817 in words is "nine hundred twenty-one million, nine hundred twenty-one thousand, eight hundred seventeen".