287561 has 4 divisors (see below), whose sum is σ = 288900. Its totient is φ = 286224.

The previous prime is 287557. The next prime is 287579. The reversal of 287561 is 165782.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 165782 = 2 ⋅82891.

It can be written as a sum of positive squares in 2 ways, for example, as 67600 + 219961 = 260^2 + 469^2 .

It is a cyclic number.

It is not a de Polignac number, because 287561 - 2² = 287557 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 287561.

It is not an unprimeable number, because it can be changed into a prime (287501) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 266 + ... + 803.

It is an arithmetic number, because the mean of its divisors is an integer number (72225).

2²⁸⁷⁵⁶¹ is an apocalyptic number.

It is an amenable number.

287561 is a deficient number, since it is larger than the sum of its proper divisors (1339).

287561 is a wasteful number, since it uses less digits than its factorization.

287561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1338.

The product of its digits is 3360, while the sum is 29.

The square root of 287561 is about 536.2471445145. The cubic root of 287561 is about 66.0049736074.

It can be divided in two parts, 287 and 561, that added together give a palindrome (848).

The spelling of 287561 in words is "two hundred eighty-seven thousand, five hundred sixty-one".