21224217 has 16 divisors (see below), whose sum is σ = 32455040. Its totient is φ = 12085632.

The previous prime is 21224207. The next prime is 21224249. The reversal of 21224217 is 71242212.

It is not a de Polignac number, because 21224217 - 2¹⁰ = 21223193 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21224193 and 21224202.

It is not an unprimeable number, because it can be changed into a prime (21224207) 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 15 ways as a sum of consecutive naturals, for example, 4959 + ... + 8187.

It is an arithmetic number, because the mean of its divisors is an integer number (2028440).

Almost surely, 2^21224217 is an apocalyptic number.

It is an amenable number.

21224217 is a deficient number, since it is larger than the sum of its proper divisors (11230823).

21224217 is a wasteful number, since it uses less digits than its factorization.

21224217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3552.

The product of its digits is 448, while the sum is 21.

The square root of 21224217 is about 4606.9748208559. The cubic root of 21224217 is about 276.8708447487.

Adding to 21224217 its reverse (71242212), we get a palindrome (92466429).

The spelling of 21224217 in words is "twenty-one million, two hundred twenty-four thousand, two hundred seventeen".