644947263405 has 24 divisors (see below), whose sum is σ = 1118011471512. Its totient is φ = 343940217984.

The previous prime is 644947263341. The next prime is 644947263407. The reversal of 644947263405 is 504362749446.

It can be written as a sum of positive squares in 4 ways, for example, as 54690031881 + 590257231524 = 233859^2 + 768282^2 .

It is not a de Polignac number, because 644947263405 - 2⁶ = 644947263341 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644947263407) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 160954 + ... + 1147083.

It is an arithmetic number, because the mean of its divisors is an integer number (46583811313).

Almost surely, 2^644947263405 is an apocalyptic number.

It is an amenable number.

644947263405 is a deficient number, since it is larger than the sum of its proper divisors (473064208107).

644947263405 is a wasteful number, since it uses less digits than its factorization.

644947263405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1319005 (or 1319002 counting only the distinct ones).

The product of its (nonzero) digits is 17418240, while the sum is 54.

The spelling of 644947263405 in words is "six hundred forty-four billion, nine hundred forty-seven million, two hundred sixty-three thousand, four hundred five".