261688 has 16 divisors (see below), whose sum is σ = 560880. Its totient is φ = 112128.

The previous prime is 261673. The next prime is 261697. The reversal of 261688 is 886162.

It is a zygodrome in base 2.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2281 + ... + 2392.

It is an arithmetic number, because the mean of its divisors is an integer number (35055).

2²⁶¹⁶⁸⁸ is an apocalyptic number.

261688 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

261688 is an abundant number, since it is smaller than the sum of its proper divisors (299192).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

261688 is a wasteful number, since it uses less digits than its factorization.

261688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4686 (or 4682 counting only the distinct ones).

The product of its digits is 4608, while the sum is 31.

The square root of 261688 is about 511.5544936759. The cubic root of 261688 is about 63.9628690869.

It can be divided in two parts, 2616 and 88, that added together give a square (2704 = 52²).

The spelling of 261688 in words is "two hundred sixty-one thousand, six hundred eighty-eight".