6444641621 has 12 divisors (see below), whose sum is σ = 7256560332. Its totient is φ = 5715864000.

The previous prime is 6444641617. The next prime is 6444641647. The reversal of 6444641621 is 1261464446.

It can be written as a sum of positive squares in 2 ways, for example, as 1657385521 + 4787256100 = 40711^2 + 69190^2 .

It is not a de Polignac number, because 6444641621 - 2² = 6444641617 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 (6444641681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 644570 + ... + 654491.

It is an arithmetic number, because the mean of its divisors is an integer number (604713361).

Almost surely, 2^6444641621 is an apocalyptic number.

It is an amenable number.

6444641621 is a deficient number, since it is larger than the sum of its proper divisors (811918711).

6444641621 is a wasteful number, since it uses less digits than its factorization.

6444641621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1299124 (or 1299113 counting only the distinct ones).

The product of its digits is 110592, while the sum is 38.

The square root of 6444641621 is about 80278.5252791804. The cubic root of 6444641621 is about 1860.9423695212.

The spelling of 6444641621 in words is "six billion, four hundred forty-four million, six hundred forty-one thousand, six hundred twenty-one".