21243147 has 4 divisors (see below), whose sum is σ = 28324200. Its totient is φ = 14162096.

The previous prime is 21243139. The next prime is 21243151. The reversal of 21243147 is 74134212.

It is a happy number.

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 21243147 - 2³ = 21243139 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21243137) 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, 3540522 + ... + 3540527.

It is an arithmetic number, because the mean of its divisors is an integer number (7081050).

Almost surely, 2^21243147 is an apocalyptic number.

21243147 is a deficient number, since it is larger than the sum of its proper divisors (7081053).

21243147 is an equidigital number, since it uses as much as digits as its factorization.

21243147 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7081052.

The product of its digits is 1344, while the sum is 24.

The square root of 21243147 is about 4609.0288564946. The cubic root of 21243147 is about 276.9531345164.

Adding to 21243147 its reverse (74134212), we get a palindrome (95377359).

The spelling of 21243147 in words is "twenty-one million, two hundred forty-three thousand, one hundred forty-seven".