21543242 has 12 divisors (see below), whose sum is σ = 37590930. Its totient is φ = 9232776.

The previous prime is 21543241. The next prime is 21543271. The reversal of 21543242 is 24234512.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 19018321 + 2524921 = 4361^2 + 1589^2 .

It is a super-2 number, since 2×21543242² = 928222551741128, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21543241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 109817 + ... + 110012.

Almost surely, 2^21543242 is an apocalyptic number.

21543242 is a deficient number, since it is larger than the sum of its proper divisors (16047688).

21543242 is a wasteful number, since it uses less digits than its factorization.

21543242 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 219845 (or 219838 counting only the distinct ones).

The product of its digits is 1920, while the sum is 23.

The square root of 21543242 is about 4641.4698103079. The cubic root of 21543242 is about 278.2511833606.

Adding to 21543242 its reverse (24234512), we get a palindrome (45777754).

The spelling of 21543242 in words is "twenty-one million, five hundred forty-three thousand, two hundred forty-two".