671286778821 has 6 divisors (see below), whose sum is σ = 969636458310. Its totient is φ = 447524519208.

The previous prime is 671286778817. The next prime is 671286778823. The reversal of 671286778821 is 128877682176.

It can be written as a sum of positive squares in only one way, i.e., 379654377921 + 291632400900 = 616161^2 + 540030^2 .

It is not a de Polignac number, because 671286778821 - 2² = 671286778817 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (671286778823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 37293709926 + ... + 37293709943.

It is an arithmetic number, because the mean of its divisors is an integer number (161606076385).

Almost surely, 2^671286778821 is an apocalyptic number.

It is an amenable number.

671286778821 is a deficient number, since it is larger than the sum of its proper divisors (298349679489).

671286778821 is a wasteful number, since it uses less digits than its factorization.

671286778821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74587419875 (or 74587419872 counting only the distinct ones).

The product of its digits is 25288704, while the sum is 63.

The spelling of 671286778821 in words is "six hundred seventy-one billion, two hundred eighty-six million, seven hundred seventy-eight thousand, eight hundred twenty-one".