644431 has 2 divisors, whose sum is σ = 644432. Its totient is φ = 644430.

The previous prime is 644411. The next prime is 644443. The reversal of 644431 is 134446.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644431 - 2⁹ = 643919 is a prime.

It is a super-2 number, since 2×644431² = 830582627522, which contains 22 as substring.

It is a Chen prime.

644431 is a lucky number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644401) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322215 + 322216.

It is an arithmetic number, because the mean of its divisors is an integer number (322216).

2⁶⁴⁴⁴³¹ is an apocalyptic number.

644431 is a deficient number, since it is larger than the sum of its proper divisors (1).

644431 is an equidigital number, since it uses as much as digits as its factorization.

644431 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1152, while the sum is 22.

The square root of 644431 is about 802.7645981233. The cubic root of 644431 is about 86.3758116303.

Adding to 644431 its reverse (134446), we get a palindrome (778877).

The spelling of 644431 in words is "six hundred forty-four thousand, four hundred thirty-one".