644261 has 2 divisors, whose sum is σ = 644262. Its totient is φ = 644260.

The previous prime is 644257. The next prime is 644291. The reversal of 644261 is 162446.

It is a happy number.

644261 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 591361 + 52900 = 769^2 + 230^2 .

It is a cyclic number.

It is not a de Polignac number, because 644261 - 2² = 644257 is a prime.

It is a super-2 number, since 2×644261² = 830144472242, which contains 22 as substring.

It is a Chen prime.

It is a d-powerful number, because it can be written as 6⁵ + 4 + 2¹⁹ + 4⁸ + 6⁶ + 1 .

It is equal to p₅₂₃₈₅ and since 644261 and 52385 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322130 + 322131.

It is an arithmetic number, because the mean of its divisors is an integer number (322131).

2⁶⁴⁴²⁶¹ is an apocalyptic number.

It is an amenable number.

644261 is a deficient number, since it is larger than the sum of its proper divisors (1).

644261 is an equidigital number, since it uses as much as digits as its factorization.

644261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1152, while the sum is 23.

The square root of 644261 is about 802.6587070480. The cubic root of 644261 is about 86.3682156894.

The spelling of 644261 in words is "six hundred forty-four thousand, two hundred sixty-one".