856421 has 2 divisors, whose sum is σ = 856422. Its totient is φ = 856420.

The previous prime is 856417. The next prime is 856441. The reversal of 856421 is 124658.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 835396 + 21025 = 914^2 + 145^2 .

It is a cyclic number.

It is not a de Polignac number, because 856421 - 2² = 856417 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (856411) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 428210 + 428211.

It is an arithmetic number, because the mean of its divisors is an integer number (428211).

2⁸⁵⁶⁴²¹ is an apocalyptic number.

It is an amenable number.

856421 is a deficient number, since it is larger than the sum of its proper divisors (1).

856421 is an equidigital number, since it uses as much as digits as its factorization.

856421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1920, while the sum is 26.

The square root of 856421 is about 925.4301702452. The cubic root of 856421 is about 94.9647514660.

The spelling of 856421 in words is "eight hundred fifty-six thousand, four hundred twenty-one".