261643 has 2 divisors, whose sum is σ = 261644. Its totient is φ = 261642.

The previous prime is 261641. The next prime is 261673. The reversal of 261643 is 346162.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 261643 - 2¹ = 261641 is a prime.

Together with 261641, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (261641) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130821 + 130822.

It is an arithmetic number, because the mean of its divisors is an integer number (130822).

2²⁶¹⁶⁴³ is an apocalyptic number.

261643 is a deficient number, since it is larger than the sum of its proper divisors (1).

261643 is an equidigital number, since it uses as much as digits as its factorization.

261643 is an evil number, because the sum of its binary digits is even.

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

The square root of 261643 is about 511.5105082010. The cubic root of 261643 is about 63.9592025144.

The spelling of 261643 in words is "two hundred sixty-one thousand, six hundred forty-three".