320821 has 2 divisors, whose sum is σ = 320822. Its totient is φ = 320820.

The previous prime is 320791. The next prime is 320833. The reversal of 320821 is 128023.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 286225 + 34596 = 535^2 + 186^2 .

It is a cyclic number.

It is not a de Polignac number, because 320821 - 2⁷ = 320693 is a prime.

It is a super-2 number, since 2×320821² = 205852228082, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 320795 and 320804.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (320851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160410 + 160411.

It is an arithmetic number, because the mean of its divisors is an integer number (160411).

2³²⁰⁸²¹ is an apocalyptic number.

It is an amenable number.

320821 is a deficient number, since it is larger than the sum of its proper divisors (1).

320821 is an equidigital number, since it uses as much as digits as its factorization.

320821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 96, while the sum is 16.

The square root of 320821 is about 566.4106284314. The cubic root of 320821 is about 68.4574833396.

Adding to 320821 its reverse (128023), we get a palindrome (448844).

The spelling of 320821 in words is "three hundred twenty thousand, eight hundred twenty-one".