261686 has 4 divisors (see below), whose sum is σ = 392532. Its totient is φ = 130842.

The previous prime is 261673. The next prime is 261697. The reversal of 261686 is 686162.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 686162 = 2 ⋅343081.

It is a congruent number.

It is an unprimeable number.

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, 65420 + ... + 65423.

It is an arithmetic number, because the mean of its divisors is an integer number (98133).

2²⁶¹⁶⁸⁶ is an apocalyptic number.

261686 is a deficient number, since it is larger than the sum of its proper divisors (130846).

261686 is a wasteful number, since it uses less digits than its factorization.

261686 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 130845.

The product of its digits is 3456, while the sum is 29.

The square root of 261686 is about 511.5525388462. The cubic root of 261686 is about 63.9627061371.

The spelling of 261686 in words is "two hundred sixty-one thousand, six hundred eighty-six".