21004442 has 4 divisors (see below), whose sum is σ = 31506666. Its totient is φ = 10502220.

The previous prime is 21004387. The next prime is 21004447. The reversal of 21004442 is 24440012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 20784481 + 219961 = 4559^2 + 469^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21004442.

It is not an unprimeable number, because it can be changed into a prime (21004447) by changing a digit.

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 as a sum of consecutive naturals, namely, 5251109 + ... + 5251112.

Almost surely, 2^21004442 is an apocalyptic number.

21004442 is a deficient number, since it is larger than the sum of its proper divisors (10502224).

21004442 is a wasteful number, since it uses less digits than its factorization.

21004442 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10502223.

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

The square root of 21004442 is about 4583.0603312634. The cubic root of 21004442 is about 275.9118688718.

Adding to 21004442 its reverse (24440012), we get a palindrome (45444454).

The spelling of 21004442 in words is "twenty-one million, four thousand, four hundred forty-two".