644531 has 2 divisors, whose sum is σ = 644532. Its totient is φ = 644530.

The previous prime is 644519. The next prime is 644549. The reversal of 644531 is 135446.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644531 - 2¹⁰ = 643507 is a prime.

It is a super-2 number, since 2×644531² = 830840419922, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 644497 and 644506.

It is not a weakly prime, because it can be changed into another prime (644131) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322265 + 322266.

It is an arithmetic number, because the mean of its divisors is an integer number (322266).

2⁶⁴⁴⁵³¹ is an apocalyptic number.

644531 is a deficient number, since it is larger than the sum of its proper divisors (1).

644531 is an equidigital number, since it uses as much as digits as its factorization.

644531 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1440, while the sum is 23.

The square root of 644531 is about 802.8268804668. The cubic root of 644531 is about 86.3802792068.

Adding to 644531 its reverse (135446), we get a palindrome (779977).

The spelling of 644531 in words is "six hundred forty-four thousand, five hundred thirty-one".