671776655981 has 2 divisors, whose sum is σ = 671776655982. Its totient is φ = 671776655980.

The previous prime is 671776655959. The next prime is 671776656059. The reversal of 671776655981 is 189556677176.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 585134733481 + 86641922500 = 764941^2 + 294350^2 .

It is a cyclic number.

It is not a de Polignac number, because 671776655981 - 2²² = 671772461677 is a prime.

It is a super-2 number, since 2×671776655981² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (671776651981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 335888327990 + 335888327991.

It is an arithmetic number, because the mean of its divisors is an integer number (335888327991).

Almost surely, 2^671776655981 is an apocalyptic number.

It is an amenable number.

671776655981 is a deficient number, since it is larger than the sum of its proper divisors (1).

671776655981 is an equidigital number, since it uses as much as digits as its factorization.

671776655981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 133358400, while the sum is 68.

The spelling of 671776655981 in words is "six hundred seventy-one billion, seven hundred seventy-six million, six hundred fifty-five thousand, nine hundred eighty-one".