261669 has 4 divisors (see below), whose sum is σ = 348896. Its totient is φ = 174444.

The previous prime is 261643. The next prime is 261673. The reversal of 261669 is 966162.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 261669 - 2⁵ = 261637 is a prime.

It is a super-2 number, since 2×261669² = 136941331122, which contains 22 as substring.

It is a D-number.

It is a Duffinian number.

261669 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261619) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 43609 + ... + 43614.

It is an arithmetic number, because the mean of its divisors is an integer number (87224).

2²⁶¹⁶⁶⁹ is an apocalyptic number.

It is an amenable number.

261669 is a deficient number, since it is larger than the sum of its proper divisors (87227).

261669 is an equidigital number, since it uses as much as digits as its factorization.

261669 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87226.

The product of its digits is 3888, while the sum is 30.

The square root of 261669 is about 511.5359224923. The cubic root of 261669 is about 63.9613210298.

The spelling of 261669 in words is "two hundred sixty-one thousand, six hundred sixty-nine".