644606659876 has 27 divisors (see below), whose sum is σ = 1133655893811. Its totient is φ = 320712836544.

The previous prime is 644606659847. The next prime is 644606659883. The reversal of 644606659876 is 678956606446.

The square root of 644606659876 is 802874.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 5924380900 + 638682278976 = 76970^2 + 799176^2 .

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 367715416 + ... + 367717168.

Almost surely, 2^644606659876 is an apocalyptic number.

644606659876 is the 802874-th square number.

It is an amenable number.

644606659876 is a deficient number, since it is larger than the sum of its proper divisors (489049233935).

644606659876 is an frugal number, since it uses more digits than its factorization.

644606659876 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3968 (or 1984 counting only the distinct ones).

The product of its (nonzero) digits is 313528320, while the sum is 67.

The spelling of 644606659876 in words is "six hundred forty-four billion, six hundred six million, six hundred fifty-nine thousand, eight hundred seventy-six".