644553 has 24 divisors (see below), whose sum is σ = 1147328. Its totient is φ = 339552.

The previous prime is 644549. The next prime is 644557. The reversal of 644553 is 355446.

It is an interprime number because it is at equal distance from previous prime (644549) and next prime (644557).

It is not a de Polignac number, because 644553 - 2² = 644549 is a prime.

It is a super-3 number, since 3×644553³ = 803335866048301131, which contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (644557) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 426 + ... + 1212.

2⁶⁴⁴⁵⁵³ is an apocalyptic number.

644553 is a gapful number since it is divisible by the number (63) formed by its first and last digit.

It is an amenable number.

644553 is a deficient number, since it is larger than the sum of its proper divisors (502775).

644553 is a wasteful number, since it uses less digits than its factorization.

644553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 813 (or 810 counting only the distinct ones).

The product of its digits is 7200, while the sum is 27.

The square root of 644553 is about 802.8405819339. The cubic root of 644553 is about 86.3812620116.

Adding to 644553 its reverse (355446), we get a palindrome (999999).

The spelling of 644553 in words is "six hundred forty-four thousand, five hundred fifty-three".