213821 has 2 divisors, whose sum is σ = 213822. Its totient is φ = 213820.

The previous prime is 213799. The next prime is 213827. The reversal of 213821 is 128312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 151321 + 62500 = 389^2 + 250^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-213821 is a prime.

It is a Chen prime.

It is a plaindrome in base 14.

It is a self number, because there is not a number n which added to its sum of digits gives 213821.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 213821.

It is not a weakly prime, because it can be changed into another prime (213827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 106910 + 106911.

It is an arithmetic number, because the mean of its divisors is an integer number (106911).

2²¹³⁸²¹ is an apocalyptic number.

It is an amenable number.

213821 is a deficient number, since it is larger than the sum of its proper divisors (1).

213821 is an equidigital number, since it uses as much as digits as its factorization.

213821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 96, while the sum is 17.

The square root of 213821 is about 462.4078286535. The cubic root of 213821 is about 59.7975584660.

The spelling of 213821 in words is "two hundred thirteen thousand, eight hundred twenty-one".