2220721 has 4 divisors (see below), whose sum is σ = 2223972. Its totient is φ = 2217472.

The previous prime is 2220697. The next prime is 2220731. The reversal of 2220721 is 1270222.

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 2030625 + 190096 = 1425^2 + 436^2 .

It is a cyclic number.

It is not a de Polignac number, because 2220721 - 2⁹ = 2220209 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 2220695 and 2220704.

It is not an unprimeable number, because it can be changed into a prime (2220731) 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, 160 + ... + 2113.

It is an arithmetic number, because the mean of its divisors is an integer number (555993).

2^2220721 is an apocalyptic number.

It is an amenable number.

2220721 is a deficient number, since it is larger than the sum of its proper divisors (3251).

2220721 is an equidigital number, since it uses as much as digits as its factorization.

2220721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3250.

The product of its (nonzero) digits is 112, while the sum is 16.

The square root of 2220721 is about 1490.2083746913. The cubic root of 2220721 is about 130.4661959879.

Adding to 2220721 its reverse (1270222), we get a palindrome (3490943).

The spelling of 2220721 in words is "two million, two hundred twenty thousand, seven hundred twenty-one".