671744651821 has 16 divisors (see below), whose sum is σ = 690077646720. Its totient is φ = 653539138560.

The previous prime is 671744651803. The next prime is 671744651869. The reversal of 671744651821 is 128156447176.

It is a cyclic number.

It is not a de Polignac number, because 671744651821 - 2⁵ = 671744651789 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (671744651801) 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, 13575301 + ... + 13624693.

It is an arithmetic number, because the mean of its divisors is an integer number (43129852920).

Almost surely, 2^671744651821 is an apocalyptic number.

It is an amenable number.

671744651821 is a deficient number, since it is larger than the sum of its proper divisors (18332994899).

671744651821 is a wasteful number, since it uses less digits than its factorization.

671744651821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50676.

The product of its digits is 2257920, while the sum is 52.

The spelling of 671744651821 in words is "six hundred seventy-one billion, seven hundred forty-four million, six hundred fifty-one thousand, eight hundred twenty-one".