12221721 has 6 divisors (see below), whose sum is σ = 17653610. Its totient is φ = 8147808.

The previous prime is 12221689. The next prime is 12221749. The reversal of 12221721 is 12712221.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 10634121 + 1587600 = 3261^2 + 1260^2 .

It is not a de Polignac number, because 12221721 - 2⁵ = 12221689 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 12221694 and 12221703.

It is not an unprimeable number, because it can be changed into a prime (12221771) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 678976 + ... + 678993.

Almost surely, 2^12221721 is an apocalyptic number.

It is an amenable number.

12221721 is a deficient number, since it is larger than the sum of its proper divisors (5431889).

12221721 is a wasteful number, since it uses less digits than its factorization.

12221721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1357975 (or 1357972 counting only the distinct ones).

The product of its digits is 112, while the sum is 18.

The square root of 12221721 is about 3495.9578086699. The cubic root of 12221721 is about 230.3442921776.

Adding to 12221721 its reverse (12712221), we get a palindrome (24933942).

The spelling of 12221721 in words is "twelve million, two hundred twenty-one thousand, seven hundred twenty-one".