261881 has 2 divisors, whose sum is σ = 261882. Its totient is φ = 261880.

The previous prime is 261847. The next prime is 261887. The reversal of 261881 is 188162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 250000 + 11881 = 500^2 + 109^2 .

It is a cyclic number.

It is not a de Polignac number, because 261881 - 2¹⁰ = 260857 is a prime.

It is a super-4 number, since 4×261881⁴ (a number of 23 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 261881.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261887) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130940 + 130941.

It is an arithmetic number, because the mean of its divisors is an integer number (130941).

2²⁶¹⁸⁸¹ is an apocalyptic number.

It is an amenable number.

261881 is a deficient number, since it is larger than the sum of its proper divisors (1).

261881 is an equidigital number, since it uses as much as digits as its factorization.

261881 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 768, while the sum is 26.

The square root of 261881 is about 511.7430996115. The cubic root of 261881 is about 63.9785898436.

The spelling of 261881 in words is "two hundred sixty-one thousand, eight hundred eighty-one".