643261 has 6 divisors (see below), whose sum is σ = 658490. Its totient is φ = 628368.

The previous prime is 643243. The next prime is 643273. The reversal of 643261 is 162346.

It can be written as a sum of positive squares in 3 ways, for example, as 383161 + 260100 = 619^2 + 510^2 .

It is not a de Polignac number, because 643261 - 2¹¹ = 641213 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643231) 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 5 ways as a sum of consecutive naturals, for example, 2695 + ... + 2923.

2⁶⁴³²⁶¹ is an apocalyptic number.

It is an amenable number.

643261 is a deficient number, since it is larger than the sum of its proper divisors (15229).

643261 is an equidigital number, since it uses as much as digits as its factorization.

643261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 335 (or 282 counting only the distinct ones).

The product of its digits is 864, while the sum is 22.

The square root of 643261 is about 802.0355353723. The cubic root of 643261 is about 86.3235066143.

The spelling of 643261 in words is "six hundred forty-three thousand, two hundred sixty-one".