261864 has 24 divisors (see below), whose sum is σ = 709410. Its totient is φ = 87264.

The previous prime is 261847. The next prime is 261881. The reversal of 261864 is 468162.

261864 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (261847) and next prime (261881).

It can be written as a sum of positive squares in only one way, i.e., 260100 + 1764 = 510^2 + 42^2 .

It is a tau number, because it is divible by the number of its divisors (24).

It is a nude number because it is divisible by every one of its digits.

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 in 5 ways as a sum of consecutive naturals, for example, 1747 + ... + 1890.

2²⁶¹⁸⁶⁴ is an apocalyptic number.

261864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

261864 is an abundant number, since it is smaller than the sum of its proper divisors (447546).

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

261864 is a wasteful number, since it uses less digits than its factorization.

261864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3649 (or 3642 counting only the distinct ones).

The product of its digits is 2304, while the sum is 27.

The square root of 261864 is about 511.7264894453. The cubic root of 261864 is about 63.9772054240.

Subtracting from 261864 its product of digits (2304), we obtain a triangular number (259560 = T₇₂₀).

The spelling of 261864 in words is "two hundred sixty-one thousand, eight hundred sixty-four".