21000000444 has 24 divisors (see below), whose sum is σ = 49021015680. Its totient is φ = 6996998064.

The previous prime is 21000000443. The next prime is 21000000479. The reversal of 21000000444 is 44400000012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000000443) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 346024 + ... + 402159.

It is an arithmetic number, because the mean of its divisors is an integer number (2042542320).

Almost surely, 2^21000000444 is an apocalyptic number.

It is an amenable number.

21000000444 is an abundant number, since it is smaller than the sum of its proper divisors (28021015236).

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

21000000444 is a wasteful number, since it uses less digits than its factorization.

21000000444 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 750529 (or 750527 counting only the distinct ones).

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

Adding to 21000000444 its reverse (44400000012), we get a palindrome (65400000456).

The spelling of 21000000444 in words is "twenty-one billion, four hundred forty-four", and thus it is an aban number.