22221721 has 4 divisors (see below), whose sum is σ = 22425700. Its totient is φ = 22017744.

The previous prime is 22221709. The next prime is 22221739. The reversal of 22221721 is 12712222.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 19263321 + 2958400 = 4389^2 + 1720^2 .

It is a cyclic number.

It is not a de Polignac number, because 22221721 - 2⁷ = 22221593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (22221781) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 101826 + ... + 102043.

It is an arithmetic number, because the mean of its divisors is an integer number (5606425).

Almost surely, 2^22221721 is an apocalyptic number.

It is an amenable number.

22221721 is a deficient number, since it is larger than the sum of its proper divisors (203979).

22221721 is a wasteful number, since it uses less digits than its factorization.

22221721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 203978.

The product of its digits is 224, while the sum is 19.

The square root of 22221721 is about 4713.9920449657. The cubic root of 22221721 is about 281.1421080154.

Adding to 22221721 its reverse (12712222), we get a palindrome (34933943).

The spelling of 22221721 in words is "twenty-two million, two hundred twenty-one thousand, seven hundred twenty-one".