861209 has 4 divisors (see below), whose sum is σ = 869220. Its totient is φ = 853200.

The previous prime is 861199. The next prime is 861221. The reversal of 861209 is 902168.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 595984 + 265225 = 772^2 + 515^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-861209 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (861239) 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, 3842 + ... + 4059.

It is an arithmetic number, because the mean of its divisors is an integer number (217305).

2⁸⁶¹²⁰⁹ is an apocalyptic number.

It is an amenable number.

861209 is a deficient number, since it is larger than the sum of its proper divisors (8011).

861209 is a wasteful number, since it uses less digits than its factorization.

861209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8010.

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 861209 is about 928.0134697298. The cubic root of 861209 is about 95.1413960927.

The spelling of 861209 in words is "eight hundred sixty-one thousand, two hundred nine".