21223647 has 8 divisors (see below), whose sum is σ = 31442480. Its totient is φ = 14149080.

The previous prime is 21223637. The next prime is 21223651. The reversal of 21223647 is 74632212.

21223647 is a `hidden beast` number, since 2 + 12 + 2 + 3 + 647 = 666.

It is not a de Polignac number, because 21223647 - 2⁶ = 21223583 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 786061 = 21223647 / (2 + 1 + 2 + 2 + 3 + 6 + 4 + 7).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21223647.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21223637) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 393004 + ... + 393057.

It is an arithmetic number, because the mean of its divisors is an integer number (3930310).

Almost surely, 2^21223647 is an apocalyptic number.

21223647 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21223647 is a deficient number, since it is larger than the sum of its proper divisors (10218833).

21223647 is an equidigital number, since it uses as much as digits as its factorization.

21223647 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 786070 (or 786064 counting only the distinct ones).

The product of its digits is 4032, while the sum is 27.

The square root of 21223647 is about 4606.9129577191. The cubic root of 21223647 is about 276.8683661682.

Adding to 21223647 its reverse (74632212), we get a palindrome (95855859).

The spelling of 21223647 in words is "twenty-one million, two hundred twenty-three thousand, six hundred forty-seven".