20013221 has 2 divisors, whose sum is σ = 20013222.
Its totient is φ = 20013220.
The previous prime is 20013193. The next prime is 20013223. The reversal of 20013221 is 12231002.
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., 19228225 + 784996 = 4385^2 + 886^2
It is a cyclic number.
It is a de Polignac number, because none of the positive numbers 2k-20013221 is a prime.
Together with 20013223, it forms a pair of twin primes.
It is a Chen prime.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (20013223) by changing a digit.
It is a good prime.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10006610 + 10006611.
It is an arithmetic number, because the mean of its divisors is an integer number (10006611).
Almost surely, 220013221 is an apocalyptic number.
It is an amenable number.
20013221 is a deficient number, since it is larger than the sum of its proper divisors (1).
20013221 is an equidigital number, since it uses as much as digits as its factorization.
20013221 is an evil number, because the sum of its binary digits is even.
The product of its (nonzero) digits is 24, while the sum is 11.
The square root of 20013221 is about 4473.6138635336.
The cubic root of 20013221 is about 271.5015606769.
Adding to 20013221 its reverse (12231002), we get a palindrome (32244223).
The spelling of 20013221 in words is "twenty million, thirteen thousand, two hundred twenty-one".