21224745 has 24 divisors (see below), whose sum is σ = 38390976. Its totient is φ = 10827168.

The previous prime is 21224741. The next prime is 21224759. The reversal of 21224745 is 54742212.

It is not a de Polignac number, because 21224745 - 2² = 21224741 is a prime.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21224741) 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 23 ways as a sum of consecutive naturals, for example, 9219 + ... + 11288.

It is an arithmetic number, because the mean of its divisors is an integer number (1599624).

Almost surely, 2^21224745 is an apocalyptic number.

It is an amenable number.

21224745 is a deficient number, since it is larger than the sum of its proper divisors (17166231).

21224745 is a wasteful number, since it uses less digits than its factorization.

21224745 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20541 (or 20538 counting only the distinct ones).

The product of its digits is 4480, while the sum is 27.

The square root of 21224745 is about 4607.0321249151. The cubic root of 21224745 is about 276.8731406574.

Adding to 21224745 its reverse (54742212), we get a palindrome (75966957).

The spelling of 21224745 in words is "twenty-one million, two hundred twenty-four thousand, seven hundred forty-five".