261872 has 20 divisors (see below), whose sum is σ = 546840. Its totient is φ = 120768.

The previous prime is 261847. The next prime is 261881. The reversal of 261872 is 278162.

It is a Harshad number since it is a multiple of its sum of digits (26).

It is an Ulam number.

It is a congruent number.

It is an unprimeable number.

261872 is an untouchable number, because it is not equal to the sum of proper divisors of any 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 in 3 ways as a sum of consecutive naturals, for example, 422 + ... + 837.

It is an arithmetic number, because the mean of its divisors is an integer number (27342).

261872 is a Friedman number, since it can be written as 8^(6*1)-272, using all its digits and the basic arithmetic operations.

2²⁶¹⁸⁷² is an apocalyptic number.

It is an amenable number.

261872 is an abundant number, since it is smaller than the sum of its proper divisors (284968).

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

261872 is a wasteful number, since it uses less digits than its factorization.

261872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1280 (or 1274 counting only the distinct ones).

The product of its digits is 1344, while the sum is 26.

The square root of 261872 is about 511.7343060613. The cubic root of 261872 is about 63.9778569230.

Subtracting 261872 from its reverse (278162), we obtain a triangular number (16290 = T₁₈₀).

The spelling of 261872 in words is "two hundred sixty-one thousand, eight hundred seventy-two".