261645 has 8 divisors (see below), whose sum is σ = 418656. Its totient is φ = 139536.

The previous prime is 261643. The next prime is 261673. The reversal of 261645 is 546162.

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

It is not a de Polignac number, because 261645 - 2¹ = 261643 is a prime.

It is a super-3 number, since 3×261645³ = 53735163452733375, which contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261641) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8707 + ... + 8736.

It is an arithmetic number, because the mean of its divisors is an integer number (52332).

2²⁶¹⁶⁴⁵ is an apocalyptic number.

It is an amenable number.

261645 is a deficient number, since it is larger than the sum of its proper divisors (157011).

261645 is a wasteful number, since it uses less digits than its factorization.

261645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17451.

The product of its digits is 1440, while the sum is 24.

The square root of 261645 is about 511.5124631913. The cubic root of 261645 is about 63.9593654821.

The spelling of 261645 in words is "two hundred sixty-one thousand, six hundred forty-five".