21204742 has 16 divisors (see below), whose sum is σ = 35436240. Its totient is φ = 9448992.

The previous prime is 21204739. The next prime is 21204787. The reversal of 21204742 is 24740212.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 13308 + ... + 14815.

It is an arithmetic number, because the mean of its divisors is an integer number (2214765).

Almost surely, 2^21204742 is an apocalyptic number.

21204742 is a deficient number, since it is larger than the sum of its proper divisors (14231498).

21204742 is a wasteful number, since it uses less digits than its factorization.

21204742 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28167.

The product of its (nonzero) digits is 896, while the sum is 22.

The square root of 21204742 is about 4604.8606927897. The cubic root of 21204742 is about 276.7861347566.

Adding to 21204742 its reverse (24740212), we get a palindrome (45944954).

The spelling of 21204742 in words is "twenty-one million, two hundred four thousand, seven hundred forty-two".