668753521 has 2 divisors, whose sum is σ = 668753522. Its totient is φ = 668753520.

The previous prime is 668753489. The next prime is 668753537. The reversal of 668753521 is 125357866.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 413552896 + 255200625 = 20336^2 + 15975^2 .

It is a cyclic number.

It is not a de Polignac number, because 668753521 - 2⁵ = 668753489 is a prime.

It is not a weakly prime, because it can be changed into another prime (668751521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334376760 + 334376761.

It is an arithmetic number, because the mean of its divisors is an integer number (334376761).

Almost surely, 2^668753521 is an apocalyptic number.

It is an amenable number.

668753521 is a deficient number, since it is larger than the sum of its proper divisors (1).

668753521 is an equidigital number, since it uses as much as digits as its factorization.

668753521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 302400, while the sum is 43.

The square root of 668753521 is about 25860.2691594655. The cubic root of 668753521 is about 874.4910328738.

The spelling of 668753521 in words is "six hundred sixty-eight million, seven hundred fifty-three thousand, five hundred twenty-one".