261187 has 4 divisors (see below), whose sum is σ = 263736. Its totient is φ = 258640.

The previous prime is 261169. The next prime is 261223. The reversal of 261187 is 781162.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 781162 = 2 ⋅390581.

It is a cyclic number.

It is not a de Polignac number, because 261187 - 2⁷ = 261059 is a prime.

It is a Duffinian number.

261187 is a lucky number.

It is a nialpdrome in base 6.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261127) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1114 + ... + 1327.

It is an arithmetic number, because the mean of its divisors is an integer number (65934).

2²⁶¹¹⁸⁷ is an apocalyptic number.

261187 is a deficient number, since it is larger than the sum of its proper divisors (2549).

261187 is a wasteful number, since it uses less digits than its factorization.

261187 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2548.

The product of its digits is 672, while the sum is 25.

The square root of 261187 is about 511.0645751762. The cubic root of 261187 is about 63.9220241756.

Subtracting from 261187 its sum of digits (25), we obtain a palindrome (261162).

The spelling of 261187 in words is "two hundred sixty-one thousand, one hundred eighty-seven".