21240742 has 16 divisors (see below), whose sum is σ = 32506992. Its totient is φ = 10406880.

The previous prime is 21240719. The next prime is 21240743. The reversal of 21240742 is 24704212.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21240743) 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 7 ways as a sum of consecutive naturals, for example, 38992 + ... + 39532.

It is an arithmetic number, because the mean of its divisors is an integer number (2031687).

Almost surely, 2^21240742 is an apocalyptic number.

21240742 is a deficient number, since it is larger than the sum of its proper divisors (11266250).

21240742 is a wasteful number, since it uses less digits than its factorization.

21240742 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 903.

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

The square root of 21240742 is about 4608.7679481614. The cubic root of 21240742 is about 276.9426825586.

Adding to 21240742 its reverse (24704212), we get a palindrome (45944954).

The spelling of 21240742 in words is "twenty-one million, two hundred forty thousand, seven hundred forty-two".