668663721761 has 16 divisors (see below), whose sum is σ = 778766655744. Its totient is φ = 562210144704.

The previous prime is 668663721757. The next prime is 668663721779. The reversal of 668663721761 is 167127366866.

It is a cyclic number.

It is not a de Polignac number, because 668663721761 - 2² = 668663721757 is a prime.

It is a super-2 number, since 2×668663721761² (a number of 24 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 668663721761.

It is not an unprimeable number, because it can be changed into a prime (668663721461) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1635215 + ... + 2002811.

It is an arithmetic number, because the mean of its divisors is an integer number (48672915984).

Almost surely, 2^668663721761 is an apocalyptic number.

It is an amenable number.

668663721761 is a deficient number, since it is larger than the sum of its proper divisors (110102933983).

668663721761 is a wasteful number, since it uses less digits than its factorization.

668663721761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 372560.

The product of its digits is 18289152, while the sum is 59.

The spelling of 668663721761 in words is "six hundred sixty-eight billion, six hundred sixty-three million, seven hundred twenty-one thousand, seven hundred sixty-one".