261555 has 32 divisors (see below), whose sum is σ = 497664. Its totient is φ = 114816.

The previous prime is 261529. The next prime is 261557. The reversal of 261555 is 555162.

It is not a de Polignac number, because 261555 - 2⁵ = 261523 is a prime.

It is a super-2 number, since 2×261555² = 136822036050, which contains 22 as substring.

It is an Ulam number.

It is a nialpdrome in base 8.

It is not an unprimeable number, because it can be changed into a prime (261557) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4909 + ... + 4961.

It is an arithmetic number, because the mean of its divisors is an integer number (15552).

2²⁶¹⁵⁵⁵ is an apocalyptic number.

261555 is a deficient number, since it is larger than the sum of its proper divisors (236109).

261555 is a wasteful number, since it uses less digits than its factorization.

261555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115.

The product of its digits is 1500, while the sum is 24.

The square root of 261555 is about 511.4244812287. The cubic root of 261555 is about 63.9520311129.

The spelling of 261555 in words is "two hundred sixty-one thousand, five hundred fifty-five".