13221721 has 8 divisors (see below), whose sum is σ = 13595400. Its totient is φ = 12850560.

The previous prime is 13221697. The next prime is 13221737. The reversal of 13221721 is 12712231.

It can be written as a sum of positive squares in 4 ways, for example, as 1225 + 13220496 = 35^2 + 3636^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 13221721 - 2⁹ = 13221209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (13221781) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15535 + ... + 16363.

It is an arithmetic number, because the mean of its divisors is an integer number (1699425).

Almost surely, 2^13221721 is an apocalyptic number.

It is an amenable number.

13221721 is a deficient number, since it is larger than the sum of its proper divisors (373679).

13221721 is an equidigital number, since it uses as much as digits as its factorization.

13221721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1259.

The product of its digits is 168, while the sum is 19.

The square root of 13221721 is about 3636.1684504434. The cubic root of 13221721 is about 236.4627101745.

Adding to 13221721 its reverse (12712231), we get a palindrome (25933952).

The spelling of 13221721 in words is "thirteen million, two hundred twenty-one thousand, seven hundred twenty-one".