261815 has 4 divisors (see below), whose sum is σ = 314184. Its totient is φ = 209448.

The previous prime is 261799. The next prime is 261823. The reversal of 261815 is 518162.

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 261815 - 2⁴ = 261799 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26177 + ... + 26186.

It is an arithmetic number, because the mean of its divisors is an integer number (78546).

2²⁶¹⁸¹⁵ is an apocalyptic number.

261815 is a deficient number, since it is larger than the sum of its proper divisors (52369).

261815 is an equidigital number, since it uses as much as digits as its factorization.

261815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52368.

The product of its digits is 480, while the sum is 23.

The square root of 261815 is about 511.6786100669. The cubic root of 261815 is about 63.9732147028.

Adding to 261815 its reverse (518162), we get a palindrome (779977).

The spelling of 261815 in words is "two hundred sixty-one thousand, eight hundred fifteen".