644532641807 has 4 divisors (see below), whose sum is σ = 648637945416. Its totient is φ = 640427338200.

The previous prime is 644532641803. The next prime is 644532641813. The reversal of 644532641807 is 708146235446.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 644532641807 - 2² = 644532641803 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 (644532641803) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2052651569 + ... + 2052651882.

It is an arithmetic number, because the mean of its divisors is an integer number (162159486354).

Almost surely, 2^644532641807 is an apocalyptic number.

644532641807 is a deficient number, since it is larger than the sum of its proper divisors (4105303609).

644532641807 is a wasteful number, since it uses less digits than its factorization.

644532641807 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4105303608.

The product of its (nonzero) digits is 3870720, while the sum is 50.

The spelling of 644532641807 in words is "six hundred forty-four billion, five hundred thirty-two million, six hundred forty-one thousand, eight hundred seven".