261145 has 8 divisors (see below), whose sum is σ = 324360. Its totient is φ = 201600.

The previous prime is 261127. The next prime is 261167. The reversal of 261145 is 541162.

It can be written as a sum of positive squares in 4 ways, for example, as 4096 + 257049 = 64^2 + 507^2 .

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

It is not a de Polignac number, because 261145 - 2⁷ = 261017 is a prime.

It is a super-2 number, since 2×261145² = 136393422050, which contains 22 as substring.

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 7 ways as a sum of consecutive naturals, for example, 756 + ... + 1045.

It is an arithmetic number, because the mean of its divisors is an integer number (40545).

261145 is a Friedman number, since it can be written as 511^2+6*4, using all its digits and the basic arithmetic operations.

2²⁶¹¹⁴⁵ is an apocalyptic number.

It is an amenable number.

261145 is a deficient number, since it is larger than the sum of its proper divisors (63215).

261145 is a wasteful number, since it uses less digits than its factorization.

261145 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1835.

The product of its digits is 240, while the sum is 19.

The square root of 261145 is about 511.0234828264. The cubic root of 261145 is about 63.9185976792.

It can be divided in two parts, 261 and 145, that added together give a triangular number (406 = T₂₈).

The spelling of 261145 in words is "two hundred sixty-one thousand, one hundred forty-five".