663981217 has 2 divisors, whose sum is σ = 663981218. Its totient is φ = 663981216.

The previous prime is 663981161. The next prime is 663981233. The reversal of 663981217 is 712189366.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 644347456 + 19633761 = 25384^2 + 4431^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-663981217 is a prime.

It is not a weakly prime, because it can be changed into another prime (663981517) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 331990608 + 331990609.

It is an arithmetic number, because the mean of its divisors is an integer number (331990609).

Almost surely, 2^663981217 is an apocalyptic number.

It is an amenable number.

663981217 is a deficient number, since it is larger than the sum of its proper divisors (1).

663981217 is an equidigital number, since it uses as much as digits as its factorization.

663981217 is an evil number, because the sum of its binary digits is even.

The product of its digits is 108864, while the sum is 43.

The square root of 663981217 is about 25767.8329899897. The cubic root of 663981217 is about 872.4059080313.

The spelling of 663981217 in words is "six hundred sixty-three million, nine hundred eighty-one thousand, two hundred seventeen".