21243242 has 4 divisors (see below), whose sum is σ = 31864866. Its totient is φ = 10621620.

The previous prime is 21243227. The next prime is 21243253. The reversal of 21243242 is 24234212.

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

It can be written as a sum of positive squares in only one way, i.e., 21242881 + 361 = 4609^2 + 19^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5310809 + ... + 5310812.

Almost surely, 2^21243242 is an apocalyptic number.

21243242 is a deficient number, since it is larger than the sum of its proper divisors (10621624).

21243242 is a wasteful number, since it uses less digits than its factorization.

21243242 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10621623.

The product of its digits is 768, while the sum is 20.

The square root of 21243242 is about 4609.0391623418. The cubic root of 21243242 is about 276.9535473634.

Adding to 21243242 its reverse (24234212), we get a palindrome (45477454).

The spelling of 21243242 in words is "twenty-one million, two hundred forty-three thousand, two hundred forty-two".