21224747 has 4 divisors (see below), whose sum is σ = 21243816. Its totient is φ = 21205680.

The previous prime is 21224741. The next prime is 21224759. The reversal of 21224747 is 74742212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21224747 - 2¹⁰ = 21223723 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21224741) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7754 + ... + 10127.

It is an arithmetic number, because the mean of its divisors is an integer number (5310954).

Almost surely, 2^21224747 is an apocalyptic number.

21224747 is a deficient number, since it is larger than the sum of its proper divisors (19069).

21224747 is a wasteful number, since it uses less digits than its factorization.

21224747 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19068.

The product of its digits is 6272, while the sum is 29.

The square root of 21224747 is about 4607.0323419746. The cubic root of 21224747 is about 276.8731493540.

Adding to 21224747 its reverse (74742212), we get a palindrome (95966959).

The spelling of 21224747 in words is "twenty-one million, two hundred twenty-four thousand, seven hundred forty-seven".