261539 has 4 divisors (see below), whose sum is σ = 267960. Its totient is φ = 255120.

The previous prime is 261529. The next prime is 261557. The reversal of 261539 is 935162.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 261539 - 2⁴ = 261523 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 8.

It is not an unprimeable number, because it can be changed into a prime (261509) by changing a digit.

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, 3149 + ... + 3230.

It is an arithmetic number, because the mean of its divisors is an integer number (66990).

2²⁶¹⁵³⁹ is an apocalyptic number.

261539 is a deficient number, since it is larger than the sum of its proper divisors (6421).

261539 is an equidigital number, since it uses as much as digits as its factorization.

261539 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6420.

The product of its digits is 1620, while the sum is 26.

The square root of 261539 is about 511.4088384062. The cubic root of 261539 is about 63.9507270489.

It can be divided in two parts, 26153 and 9, that added together give a palindrome (26162).

The spelling of 261539 in words is "two hundred sixty-one thousand, five hundred thirty-nine".