644555441261 has 8 divisors (see below), whose sum is σ = 661025805048. Its totient is φ = 628120768000.

The previous prime is 644555441251. The next prime is 644555441287. The reversal of 644555441261 is 162144555446.

644555441261 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 23185848361 + 621369592900 = 152269^2 + 788270^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644555441261 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 (644555441251) 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, 8886050 + ... + 8958291.

It is an arithmetic number, because the mean of its divisors is an integer number (82628225631).

Almost surely, 2^644555441261 is an apocalyptic number.

It is an amenable number.

644555441261 is a deficient number, since it is larger than the sum of its proper divisors (16470363787).

644555441261 is a wasteful number, since it uses less digits than its factorization.

644555441261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17845263.

The product of its digits is 2304000, while the sum is 47.

The spelling of 644555441261 in words is "six hundred forty-four billion, five hundred fifty-five million, four hundred forty-one thousand, two hundred sixty-one".