221813 has 2 divisors, whose sum is σ = 221814. Its totient is φ = 221812.

The previous prime is 221807. The next prime is 221827. The reversal of 221813 is 318122.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 174724 + 47089 = 418^2 + 217^2 .

It is a cyclic number.

It is not a de Polignac number, because 221813 - 2⁴ = 221797 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 221791 and 221800.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221873) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110906 + 110907.

It is an arithmetic number, because the mean of its divisors is an integer number (110907).

2²²¹⁸¹³ is an apocalyptic number.

It is an amenable number.

221813 is a deficient number, since it is larger than the sum of its proper divisors (1).

221813 is an equidigital number, since it uses as much as digits as its factorization.

221813 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 221813 is about 470.9702750705. The cubic root of 221813 is about 60.5334832755.

Adding to 221813 its reverse (318122), we get a palindrome (539935).

The spelling of 221813 in words is "two hundred twenty-one thousand, eight hundred thirteen".