21304242 has 16 divisors (see below), whose sum is σ = 47342880. Its totient is φ = 7101396.

The previous prime is 21304237. The next prime is 21304253. The reversal of 21304242 is 24240312.

It is a Harshad number since it is a multiple of its sum of digits (18).

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, 197208 + ... + 197315.

It is an arithmetic number, because the mean of its divisors is an integer number (2958930).

Almost surely, 2^21304242 is an apocalyptic number.

21304242 is an abundant number, since it is smaller than the sum of its proper divisors (26038638).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21304242 is a wasteful number, since it uses less digits than its factorization.

21304242 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 394534 (or 394528 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 21304242 is about 4615.6518499558. The cubic root of 21304242 is about 277.2183848678.

Adding to 21304242 its reverse (24240312), we get a palindrome (45544554).

The spelling of 21304242 in words is "twenty-one million, three hundred four thousand, two hundred forty-two".