856021 has 2 divisors, whose sum is σ = 856022. Its totient is φ = 856020.

The previous prime is 855997. The next prime is 856043. The reversal of 856021 is 120658.

It is a happy number.

It is an a-pointer prime, because the next prime (856043) can be obtained adding 856021 to its sum of digits (22).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 703921 + 152100 = 839^2 + 390^2 .

It is a cyclic number.

It is not a de Polignac number, because 856021 - 2⁵ = 855989 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 855983 and 856001.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (856061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 428010 + 428011.

It is an arithmetic number, because the mean of its divisors is an integer number (428011).

2⁸⁵⁶⁰²¹ is an apocalyptic number.

It is an amenable number.

856021 is a deficient number, since it is larger than the sum of its proper divisors (1).

856021 is an equidigital number, since it uses as much as digits as its factorization.

856021 is an evil number, because the sum of its binary digits is even.

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

The square root of 856021 is about 925.2140292927. The cubic root of 856021 is about 94.9499644178.

Adding to 856021 its reverse (120658), we get a palindrome (976679).

The spelling of 856021 in words is "eight hundred fifty-six thousand, twenty-one".