261686881 has 2 divisors, whose sum is σ = 261686882. Its totient is φ = 261686880.

The previous prime is 261686837. The next prime is 261686897. The reversal of 261686881 is 188686162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 194184225 + 67502656 = 13935^2 + 8216^2 .

It is a cyclic number.

It is not a de Polignac number, because 261686881 - 2¹⁹ = 261162593 is a prime.

It is a super-2 number, since 2×261686881² = 136960047375016322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (261626881) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130843440 + 130843441.

It is an arithmetic number, because the mean of its divisors is an integer number (130843441).

Almost surely, 2^261686881 is an apocalyptic number.

It is an amenable number.

261686881 is a deficient number, since it is larger than the sum of its proper divisors (1).

261686881 is an equidigital number, since it uses as much as digits as its factorization.

261686881 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 221184, while the sum is 46.

The square root of 261686881 is about 16176.7388864381. The cubic root of 261686881 is about 639.6277791656.

The spelling of 261686881 in words is "two hundred sixty-one million, six hundred eighty-six thousand, eight hundred eighty-one".