221021 has 2 divisors, whose sum is σ = 221022.
Its totient is φ = 221020.
The previous prime is 220973. The next prime is 221047. The reversal of 221021 is 120122.
It is a strong prime.
It can be written as a sum of positive squares in only one way, i.e., 220900 + 121 = 470^2 + 11^2
It is a cyclic number.
It is a de Polignac number, because none of the positive numbers 2k-221021 is a prime.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (221071) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (13) of ones.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110510 + 110511.
It is an arithmetic number, because the mean of its divisors is an integer number (110511).
2221021 is an apocalyptic number.
It is an amenable number.
221021 is a deficient number, since it is larger than the sum of its proper divisors (1).
221021 is an equidigital number, since it uses as much as digits as its factorization.
221021 is an odious number, because the sum of its binary digits is odd.
The product of its (nonzero) digits is 8, while the sum is 8.
The square root of 221021 is about 470.1287057817.
The cubic root of 221021 is about 60.4613509042.
Adding to 221021 its reverse (120122), we get a palindrome (341143).
The spelling of 221021 in words is "two hundred twenty-one thousand, twenty-one", and thus it is an iban number.