261641 has 2 divisors, whose sum is σ = 261642. Its totient is φ = 261640.

The previous prime is 261637. The next prime is 261643. The reversal of 261641 is 146162.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 246016 + 15625 = 496^2 + 125^2 .

It is a cyclic number.

It is not a de Polignac number, because 261641 - 2² = 261637 is a prime.

Together with 261643, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (261643) 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 as a sum of consecutive naturals, namely, 130820 + 130821.

It is an arithmetic number, because the mean of its divisors is an integer number (130821).

2²⁶¹⁶⁴¹ is an apocalyptic number.

It is an amenable number.

261641 is a deficient number, since it is larger than the sum of its proper divisors (1).

261641 is an equidigital number, since it uses as much as digits as its factorization.

261641 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 288, while the sum is 20.

The square root of 261641 is about 511.5085532032. The cubic root of 261641 is about 63.9590395458.

The spelling of 261641 in words is "two hundred sixty-one thousand, six hundred forty-one".