21204642 has 16 divisors (see below), whose sum is σ = 42799680. Its totient is φ = 7003152.

The previous prime is 21204641. The next prime is 21204679. The reversal of 21204642 is 24640212.

It is not an unprimeable number, because it can be changed into a prime (21204641) 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, 15558 + ... + 16865.

It is an arithmetic number, because the mean of its divisors is an integer number (2674980).

Almost surely, 2^21204642 is an apocalyptic number.

21204642 is an abundant number, since it is smaller than the sum of its proper divisors (21595038).

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

21204642 is a wasteful number, since it uses less digits than its factorization.

21204642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32537.

The product of its (nonzero) digits is 768, while the sum is 21.

The square root of 21204642 is about 4604.8498346852. The cubic root of 21204642 is about 276.7856996549.

Adding to 21204642 its reverse (24640212), we get a palindrome (45844854).

The spelling of 21204642 in words is "twenty-one million, two hundred four thousand, six hundred forty-two".