2218721 has 4 divisors (see below), whose sum is σ = 2349252. Its totient is φ = 2088192.

The previous prime is 2218709. The next prime is 2218751. The reversal of 2218721 is 1278122.

2218721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 1677025 + 541696 = 1295^2 + 736^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2218721 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2218751) 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 in 3 ways as a sum of consecutive naturals, for example, 65240 + ... + 65273.

It is an arithmetic number, because the mean of its divisors is an integer number (587313).

2^2218721 is an apocalyptic number.

It is an amenable number.

2218721 is a deficient number, since it is larger than the sum of its proper divisors (130531).

2218721 is a wasteful number, since it uses less digits than its factorization.

2218721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 130530.

The product of its digits is 448, while the sum is 23.

The square root of 2218721 is about 1489.5371764411. The cubic root of 2218721 is about 130.4270179065.

The spelling of 2218721 in words is "two million, two hundred eighteen thousand, seven hundred twenty-one".