261779 has 4 divisors (see below), whose sum is σ = 299184. Its totient is φ = 224376.

The previous prime is 261773. The next prime is 261787. The reversal of 261779 is 977162.

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 261779 - 2⁸ = 261523 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261773) 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, 18692 + ... + 18705.

It is an arithmetic number, because the mean of its divisors is an integer number (74796).

2²⁶¹⁷⁷⁹ is an apocalyptic number.

261779 is a deficient number, since it is larger than the sum of its proper divisors (37405).

261779 is an equidigital number, since it uses as much as digits as its factorization.

261779 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37404.

The product of its digits is 5292, while the sum is 32.

The square root of 261779 is about 511.6434305256. The cubic root of 261779 is about 63.9702824271.

The spelling of 261779 in words is "two hundred sixty-one thousand, seven hundred seventy-nine".