531821 has 2 divisors, whose sum is σ = 531822. Its totient is φ = 531820.

The previous prime is 531799. The next prime is 531823. The reversal of 531821 is 128135.

531821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 346921 + 184900 = 589^2 + 430^2 .

It is a cyclic number.

It is not a de Polignac number, because 531821 - 2¹⁰ = 530797 is a prime.

Together with 531823, it forms a pair of twin primes.

It is a Chen prime.

It is a nialpdrome in base 14.

It is a junction number, because it is equal to n+sod(n) for n = 531793 and 531802.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (531823) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 265910 + 265911.

It is an arithmetic number, because the mean of its divisors is an integer number (265911).

2⁵³¹⁸²¹ is an apocalyptic number.

It is an amenable number.

531821 is a deficient number, since it is larger than the sum of its proper divisors (1).

531821 is an equidigital number, since it uses as much as digits as its factorization.

531821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 240, while the sum is 20.

The square root of 531821 is about 729.2605844278. The cubic root of 531821 is about 81.0193014004.

Adding to 531821 its reverse (128135), we get a palindrome (659956).

The spelling of 531821 in words is "five hundred thirty-one thousand, eight hundred twenty-one".