21440042 has 16 divisors (see below), whose sum is σ = 34853280. Its totient is φ = 9832752.

The previous prime is 21440039. The next prime is 21440051. The reversal of 21440042 is 24004412.

It is a self number, because there is not a number n which added to its sum of digits gives 21440042.

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, 1709 + ... + 6767.

It is an arithmetic number, because the mean of its divisors is an integer number (2178330).

Almost surely, 2^21440042 is an apocalyptic number.

21440042 is a deficient number, since it is larger than the sum of its proper divisors (13413238).

21440042 is a wasteful number, since it uses less digits than its factorization.

21440042 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5237.

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

The square root of 21440042 is about 4630.3392964231. The cubic root of 21440042 is about 277.8061637243.

Adding to 21440042 its reverse (24004412), we get a palindrome (45444454).

The spelling of 21440042 in words is "twenty-one million, four hundred forty thousand, forty-two".