644398917121 has 8 divisors (see below), whose sum is σ = 648661944744. Its totient is φ = 640145909760.

The previous prime is 644398917109. The next prime is 644398917131. The reversal of 644398917121 is 121719893446.

It can be written as a sum of positive squares in 4 ways, for example, as 334332586225 + 310066330896 = 578215^2 + 556836^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 644398917121 - 2¹¹ = 644398915073 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644398917131) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2376000 + ... + 2633281.

It is an arithmetic number, because the mean of its divisors is an integer number (81082743093).

Almost surely, 2^644398917121 is an apocalyptic number.

It is an amenable number.

644398917121 is a deficient number, since it is larger than the sum of its proper divisors (4263027623).

644398917121 is a wasteful number, since it uses less digits than its factorization.

644398917121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5010131.

The product of its digits is 2612736, while the sum is 55.

The spelling of 644398917121 in words is "six hundred forty-four billion, three hundred ninety-eight million, nine hundred seventeen thousand, one hundred twenty-one".