21042242 has 16 divisors (see below), whose sum is σ = 35089152. Its totient is φ = 9398160.

The previous prime is 21042223. The next prime is 21042251. The reversal of 21042242 is 24224012.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21042242.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12248 + ... + 13859.

It is an arithmetic number, because the mean of its divisors is an integer number (2193072).

Almost surely, 2^21042242 is an apocalyptic number.

21042242 is a deficient number, since it is larger than the sum of its proper divisors (14046910).

21042242 is a wasteful number, since it uses less digits than its factorization.

21042242 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26153.

The product of its (nonzero) digits is 256, while the sum is 17.

The square root of 21042242 is about 4587.1823595754. The cubic root of 21042242 is about 276.0772817962.

Adding to 21042242 its reverse (24224012), we get a palindrome (45266254).

The spelling of 21042242 in words is "twenty-one million, forty-two thousand, two hundred forty-two".