261890 has 8 divisors (see below), whose sum is σ = 471420. Its totient is φ = 104752.

The previous prime is 261887. The next prime is 261917. The reversal of 261890 is 98162.

It can be written as a sum of positive squares in 2 ways, for example, as 259081 + 2809 = 509^2 + 53^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13085 + ... + 13104.

2²⁶¹⁸⁹⁰ is an apocalyptic number.

261890 is a deficient number, since it is larger than the sum of its proper divisors (209530).

261890 is a wasteful number, since it uses less digits than its factorization.

261890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26196.

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 261890 is about 511.7518930107. The cubic root of 261890 is about 63.9793227474.

The spelling of 261890 in words is "two hundred sixty-one thousand, eight hundred ninety".