261204815 has 4 divisors (see below), whose sum is σ = 313445784. Its totient is φ = 208963848.

The previous prime is 261204787. The next prime is 261204841. The reversal of 261204815 is 518402162.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 518402162 = 2 ⋅259201081.

It is a cyclic number.

It is not a de Polignac number, because 261204815 - 2¹⁰ = 261203791 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26120477 + ... + 26120486.

It is an arithmetic number, because the mean of its divisors is an integer number (78361446).

Almost surely, 2^261204815 is an apocalyptic number.

261204815 is a deficient number, since it is larger than the sum of its proper divisors (52240969).

261204815 is an equidigital number, since it uses as much as digits as its factorization.

261204815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52240968.

The product of its (nonzero) digits is 3840, while the sum is 29.

The square root of 261204815 is about 16161.8320434287. The cubic root of 261204815 is about 639.2347747023.

Adding to 261204815 its reverse (518402162), we get a palindrome (779606977).

The spelling of 261204815 in words is "two hundred sixty-one million, two hundred four thousand, eight hundred fifteen".