2221721 has 2 divisors, whose sum is σ = 2221722. Its totient is φ = 2221720.

The previous prime is 2221711. The next prime is 2221733. The reversal of 2221721 is 1271222.

2221721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1290496 + 931225 = 1136^2 + 965^2 .

It is a cyclic number.

It is not a de Polignac number, because 2221721 - 2⁶ = 2221657 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 2221721.

It is not a weakly prime, because it can be changed into another prime (2221711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1110860 + 1110861.

It is an arithmetic number, because the mean of its divisors is an integer number (1110861).

2^2221721 is an apocalyptic number.

It is an amenable number.

2221721 is a deficient number, since it is larger than the sum of its proper divisors (1).

2221721 is an equidigital number, since it uses as much as digits as its factorization.

2221721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 112, while the sum is 17.

The square root of 2221721 is about 1490.5438604751. The cubic root of 2221721 is about 130.4857762079.

Adding to 2221721 its reverse (1271222), we get a palindrome (3492943).

The spelling of 2221721 in words is "two million, two hundred twenty-one thousand, seven hundred twenty-one".