644557707071 has 4 divisors (see below), whose sum is σ = 647932354944. Its totient is φ = 641183059200.

The previous prime is 644557706993. The next prime is 644557707103. The reversal of 644557707071 is 170707755446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 170707755446 = 2 ⋅85353877723.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644557707071 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 (644557701071) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1687323650 + ... + 1687324031.

It is an arithmetic number, because the mean of its divisors is an integer number (161983088736).

Almost surely, 2^644557707071 is an apocalyptic number.

644557707071 is a deficient number, since it is larger than the sum of its proper divisors (3374647873).

644557707071 is a wasteful number, since it uses less digits than its factorization.

644557707071 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3374647872.

The product of its (nonzero) digits is 5762400, while the sum is 53.

The spelling of 644557707071 in words is "six hundred forty-four billion, five hundred fifty-seven million, seven hundred seven thousand, seventy-one".