668921689481 has 4 divisors (see below), whose sum is σ = 669576853764. Its totient is φ = 668266525200.

The previous prime is 668921689477. The next prime is 668921689483. The reversal of 668921689481 is 184986129866.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 138762955081 + 530158734400 = 372509^2 + 728120^2 .

It is a cyclic number.

It is not a de Polignac number, because 668921689481 - 2² = 668921689477 is a prime.

It is a super-2 number, since 2×668921689481² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (668921689483) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 327580610 + ... + 327582651.

It is an arithmetic number, because the mean of its divisors is an integer number (167394213441).

Almost surely, 2^668921689481 is an apocalyptic number.

It is an amenable number.

668921689481 is a deficient number, since it is larger than the sum of its proper divisors (655164283).

668921689481 is a wasteful number, since it uses less digits than its factorization.

668921689481 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 655164282.

The product of its digits is 71663616, while the sum is 68.

The spelling of 668921689481 in words is "six hundred sixty-eight billion, nine hundred twenty-one million, six hundred eighty-nine thousand, four hundred eighty-one".