644012553 has 8 divisors (see below), whose sum is σ = 873237600. Its totient is φ = 422064608.

The previous prime is 644012533. The next prime is 644012609. The reversal of 644012553 is 355210446.

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 644012553 - 2¹⁴ = 643996169 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 644012553.

It is not an unprimeable number, because it can be changed into a prime (644012533) 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 7 ways as a sum of consecutive naturals, for example, 1819068 + ... + 1819421.

It is an arithmetic number, because the mean of its divisors is an integer number (109154700).

Almost surely, 2^644012553 is an apocalyptic number.

It is an amenable number.

644012553 is a deficient number, since it is larger than the sum of its proper divisors (229225047).

644012553 is a wasteful number, since it uses less digits than its factorization.

644012553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3638551.

The product of its (nonzero) digits is 14400, while the sum is 30.

The square root of 644012553 is about 25377.4024084420. The cubic root of 644012553 is about 863.5711217543.

Adding to 644012553 its reverse (355210446), we get a palindrome (999222999).

The spelling of 644012553 in words is "six hundred forty-four million, twelve thousand, five hundred fifty-three".