21000444 has 12 divisors (see below), whose sum is σ = 49001064. Its totient is φ = 7000144.

The previous prime is 21000433. The next prime is 21000461. The reversal of 21000444 is 44400012.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

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 3 ways as a sum of consecutive naturals, for example, 875007 + ... + 875030.

It is an arithmetic number, because the mean of its divisors is an integer number (4083422).

Almost surely, 2^21000444 is an apocalyptic number.

It is an amenable number.

21000444 is an abundant number, since it is smaller than the sum of its proper divisors (28000620).

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

21000444 is a wasteful number, since it uses less digits than its factorization.

21000444 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1750044 (or 1750042 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 15.

The square root of 21000444 is about 4582.6241390714. The cubic root of 21000444 is about 275.8943620091.

Adding to 21000444 its reverse (44400012), we get a palindrome (65400456).

The spelling of 21000444 in words is "twenty-one million, four hundred forty-four", and thus it is an aban number.