663745921 has 2 divisors, whose sum is σ = 663745922. Its totient is φ = 663745920.

The previous prime is 663745903. The next prime is 663745949. The reversal of 663745921 is 129547366.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 662341696 + 1404225 = 25736^2 + 1185^2 .

It is a cyclic number.

It is not a de Polignac number, because 663745921 - 2⁷ = 663745793 is a prime.

It is not a weakly prime, because it can be changed into another prime (663740921) 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, 331872960 + 331872961.

It is an arithmetic number, because the mean of its divisors is an integer number (331872961).

Almost surely, 2^663745921 is an apocalyptic number.

It is an amenable number.

663745921 is a deficient number, since it is larger than the sum of its proper divisors (1).

663745921 is an equidigital number, since it uses as much as digits as its factorization.

663745921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 272160, while the sum is 43.

The square root of 663745921 is about 25763.2668930010. The cubic root of 663745921 is about 872.3028439347.

The spelling of 663745921 in words is "six hundred sixty-three million, seven hundred forty-five thousand, nine hundred twenty-one".