221321209 has 2 divisors, whose sum is σ = 221321210. Its totient is φ = 221321208.

The previous prime is 221321159. The next prime is 221321251. The reversal of 221321209 is 902123122.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 200845584 + 20475625 = 14172^2 + 4525^2 .

It is a cyclic number.

It is not a de Polignac number, because 221321209 - 2¹³ = 221313017 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 221321209.

It is not a weakly prime, because it can be changed into another prime (221321279) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110660604 + 110660605.

It is an arithmetic number, because the mean of its divisors is an integer number (110660605).

Almost surely, 2^221321209 is an apocalyptic number.

It is an amenable number.

221321209 is a deficient number, since it is larger than the sum of its proper divisors (1).

221321209 is an equidigital number, since it uses as much as digits as its factorization.

221321209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 221321209 is about 14876.8682524246. The cubic root of 221321209 is about 604.8871305505.

It can be divided in two parts, 22 and 1321209, that added together give a palindrome (1321231).

The spelling of 221321209 in words is "two hundred twenty-one million, three hundred twenty-one thousand, two hundred nine".