2215721 has 4 divisors (see below), whose sum is σ = 2262912. Its totient is φ = 2168532.

The previous prime is 2215699. The next prime is 2215777. The reversal of 2215721 is 1275122.

2215721 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, 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 2215721 - 2¹⁸ = 1953577 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 2215693 and 2215702.

It is not an unprimeable number, because it can be changed into a prime (2215921) 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, 23525 + ... + 23618.

It is an arithmetic number, because the mean of its divisors is an integer number (565728).

2^2215721 is an apocalyptic number.

It is an amenable number.

2215721 is a deficient number, since it is larger than the sum of its proper divisors (47191).

2215721 is an equidigital number, since it uses as much as digits as its factorization.

2215721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47190.

The product of its digits is 280, while the sum is 20.

The square root of 2215721 is about 1488.5298115926. The cubic root of 2215721 is about 130.3682066153.

The spelling of 2215721 in words is "two million, two hundred fifteen thousand, seven hundred twenty-one".