644741663 has 4 divisors (see below), whose sum is σ = 645053568. Its totient is φ = 644429760.

The previous prime is 644741651. The next prime is 644741683. The reversal of 644741663 is 366147446.

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 644741663 - 2¹⁰ = 644740639 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644741663.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644741623) 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, 152831 + ... + 156992.

It is an arithmetic number, because the mean of its divisors is an integer number (161263392).

Almost surely, 2^644741663 is an apocalyptic number.

644741663 is a deficient number, since it is larger than the sum of its proper divisors (311905).

644741663 is a wasteful number, since it uses less digits than its factorization.

644741663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 311904.

The product of its digits is 290304, while the sum is 41.

The square root of 644741663 is about 25391.7636843131. The cubic root of 644741663 is about 863.8968922562.

The spelling of 644741663 in words is "six hundred forty-four million, seven hundred forty-one thousand, six hundred sixty-three".