644752638253 has 2 divisors, whose sum is σ = 644752638254. Its totient is φ = 644752638252.

The previous prime is 644752638227. The next prime is 644752638337. The reversal of 644752638253 is 352836257446.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 538047189289 + 106705448964 = 733517^2 + 326658^2 .

It is a cyclic number.

It is not a de Polignac number, because 644752638253 - 2²¹ = 644750541101 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 644752638194 and 644752638203.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644752638553) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322376319126 + 322376319127.

It is an arithmetic number, because the mean of its divisors is an integer number (322376319127).

Almost surely, 2^644752638253 is an apocalyptic number.

It is an amenable number.

644752638253 is a deficient number, since it is larger than the sum of its proper divisors (1).

644752638253 is an equidigital number, since it uses as much as digits as its factorization.

644752638253 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 29030400, while the sum is 55.

The spelling of 644752638253 in words is "six hundred forty-four billion, seven hundred fifty-two million, six hundred thirty-eight thousand, two hundred fifty-three".