865021 has 4 divisors (see below), whose sum is σ = 867132. Its totient is φ = 862912.

The previous prime is 865003. The next prime is 865043. The reversal of 865021 is 120568.

It is a happy number.

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 81796 + 783225 = 286^2 + 885^2 .

It is a cyclic number.

It is not a de Polignac number, because 865021 - 2⁵ = 864989 is a prime.

It is a super-2 number, since 2×865021² = 1496522660882, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 864983 and 865001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (865001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 220 + ... + 1333.

It is an arithmetic number, because the mean of its divisors is an integer number (216783).

2⁸⁶⁵⁰²¹ is an apocalyptic number.

It is an amenable number.

865021 is a deficient number, since it is larger than the sum of its proper divisors (2111).

865021 is a wasteful number, since it uses less digits than its factorization.

865021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2110.

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 865021 is about 930.0650514883. The cubic root of 865021 is about 95.2815653977.

Adding to 865021 its reverse (120568), we get a palindrome (985589).

The spelling of 865021 in words is "eight hundred sixty-five thousand, twenty-one".