21242147 has 4 divisors (see below), whose sum is σ = 21409536. Its totient is φ = 21074760.

The previous prime is 21242131. The next prime is 21242153. The reversal of 21242147 is 74124212.

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 21242147 - 2⁴ = 21242131 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21242047) 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, 83504 + ... + 83757.

It is an arithmetic number, because the mean of its divisors is an integer number (5352384).

Almost surely, 2^21242147 is an apocalyptic number.

21242147 is a deficient number, since it is larger than the sum of its proper divisors (167389).

21242147 is a wasteful number, since it uses less digits than its factorization.

21242147 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 167388.

The product of its digits is 896, while the sum is 23.

The square root of 21242147 is about 4608.9203724951. The cubic root of 21242147 is about 276.9487886838.

Adding to 21242147 its reverse (74124212), we get a palindrome (95366359).

The spelling of 21242147 in words is "twenty-one million, two hundred forty-two thousand, one hundred forty-seven".