668628721513 has 2 divisors, whose sum is σ = 668628721514. Its totient is φ = 668628721512.

The previous prime is 668628721457. The next prime is 668628721549. The reversal of 668628721513 is 315127826866.

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., 664244560144 + 4384161369 = 815012^2 + 66213^2 .

It is a cyclic number.

It is not a de Polignac number, because 668628721513 - 2²¹ = 668626624361 is a prime.

It is not a weakly prime, because it can be changed into another prime (668628721583) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334314360756 + 334314360757.

It is an arithmetic number, because the mean of its divisors is an integer number (334314360757).

Almost surely, 2^668628721513 is an apocalyptic number.

It is an amenable number.

668628721513 is a deficient number, since it is larger than the sum of its proper divisors (1).

668628721513 is an equidigital number, since it uses as much as digits as its factorization.

668628721513 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5806080, while the sum is 55.

The spelling of 668628721513 in words is "six hundred sixty-eight billion, six hundred twenty-eight million, seven hundred twenty-one thousand, five hundred thirteen".