398783921 has 2 divisors, whose sum is σ = 398783922. Its totient is φ = 398783920.

The previous prime is 398783789. The next prime is 398783929. The reversal of 398783921 is 129387893.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 334158400 + 64625521 = 18280^2 + 8039^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-398783921 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 398783921.

It is not a weakly prime, because it can be changed into another prime (398783929) 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, 199391960 + 199391961.

It is an arithmetic number, because the mean of its divisors is an integer number (199391961).

Almost surely, 2^398783921 is an apocalyptic number.

It is an amenable number.

398783921 is a deficient number, since it is larger than the sum of its proper divisors (1).

398783921 is an equidigital number, since it uses as much as digits as its factorization.

398783921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 653184, while the sum is 50.

The square root of 398783921 is about 19969.5748828061. The cubic root of 398783921 is about 736.0588628735.

The spelling of 398783921 in words is "three hundred ninety-eight million, seven hundred eighty-three thousand, nine hundred twenty-one".