865221 has 8 divisors (see below), whose sum is σ = 1318464. Its totient is φ = 494400.

The previous prime is 865217. The next prime is 865231. The reversal of 865221 is 122568.

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

It is not a de Polignac number, because 865221 - 2² = 865217 is a prime.

It is a nialpdrome in base 10.

It is a junction number, because it is equal to n+sod(n) for n = 865191 and 865200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (865201) by changing a digit.

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, 20580 + ... + 20621.

It is an arithmetic number, because the mean of its divisors is an integer number (164808).

2⁸⁶⁵²²¹ is an apocalyptic number.

It is an amenable number.

865221 is a deficient number, since it is larger than the sum of its proper divisors (453243).

865221 is a wasteful number, since it uses less digits than its factorization.

865221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41211.

The product of its digits is 960, while the sum is 24.

The square root of 865221 is about 930.1725646352. The cubic root of 865221 is about 95.2889081268.

Adding to 865221 its reverse (122568), we get a palindrome (987789).

The spelling of 865221 in words is "eight hundred sixty-five thousand, two hundred twenty-one".