2217721 has 4 divisors (see below), whose sum is σ = 2419344. Its totient is φ = 2016100.

The previous prime is 2217673. The next prime is 2217749. The reversal of 2217721 is 1277122.

2217721 = 444² + 445² + ... + 454².

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 2217721 - 2¹¹ = 2215673 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 2217692 and 2217701.

It is not an unprimeable number, because it can be changed into a prime (2217421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 100795 + ... + 100816.

It is an arithmetic number, because the mean of its divisors is an integer number (604836).

2^2217721 is an apocalyptic number.

It is an amenable number.

2217721 is a deficient number, since it is larger than the sum of its proper divisors (201623).

2217721 is a wasteful number, since it uses less digits than its factorization.

2217721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 201622.

The product of its digits is 392, while the sum is 22.

The square root of 2217721 is about 1489.2014638725. The cubic root of 2217721 is about 130.4074200365.

The spelling of 2217721 in words is "two million, two hundred seventeen thousand, seven hundred twenty-one".