261905 has 12 divisors (see below), whose sum is σ = 365940. Its totient is φ = 179424.

The previous prime is 261887. The next prime is 261917. The reversal of 261905 is 509162.

It can be written as a sum of positive squares in 2 ways, for example, as 108241 + 153664 = 329^2 + 392^2 .

It is not a de Polignac number, because 261905 - 2¹⁴ = 245521 is a prime.

It is a nialpdrome in base 8.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 290 + ... + 779.

It is an arithmetic number, because the mean of its divisors is an integer number (30495).

2²⁶¹⁹⁰⁵ is an apocalyptic number.

It is an amenable number.

261905 is a deficient number, since it is larger than the sum of its proper divisors (104035).

261905 is a wasteful number, since it uses less digits than its factorization.

261905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1088 (or 1081 counting only the distinct ones).

The product of its (nonzero) digits is 540, while the sum is 23.

The square root of 261905 is about 511.7665483402. The cubic root of 261905 is about 63.9805442163.

The spelling of 261905 in words is "two hundred sixty-one thousand, nine hundred five".