21228247 has 2 divisors, whose sum is σ = 21228248. Its totient is φ = 21228246.

The previous prime is 21228227. The next prime is 21228289. The reversal of 21228247 is 74282212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21228247 - 2¹¹ = 21226199 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21228217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10614123 + 10614124.

It is an arithmetic number, because the mean of its divisors is an integer number (10614124).

Almost surely, 2^21228247 is an apocalyptic number.

21228247 is a deficient number, since it is larger than the sum of its proper divisors (1).

21228247 is an equidigital number, since it uses as much as digits as its factorization.

21228247 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3584, while the sum is 28.

The square root of 21228247 is about 4607.4121803893. The cubic root of 21228247 is about 276.8883674822. Note that the first 3 decimals are identical.

The spelling of 21228247 in words is "twenty-one million, two hundred twenty-eight thousand, two hundred forty-seven".