261806 has 8 divisors (see below), whose sum is σ = 397920. Its totient is φ = 129168.

The previous prime is 261799. The next prime is 261823. The reversal of 261806 is 608162.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 261806.

It is an unprimeable number.

261806 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 671 + ... + 986.

It is an arithmetic number, because the mean of its divisors is an integer number (49740).

2²⁶¹⁸⁰⁶ is an apocalyptic number.

261806 is a deficient number, since it is larger than the sum of its proper divisors (136114).

261806 is a wasteful number, since it uses less digits than its factorization.

261806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1738.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 261806 is about 511.6698154083. The cubic root of 261806 is about 63.9724816591.

Adding to 261806 its reverse (608162), we get a palindrome (869968).

It can be divided in two parts, 26180 and 6, that multiplied together give a triangular number (157080 = T₅₆₀).

The spelling of 261806 in words is "two hundred sixty-one thousand, eight hundred six".