21000443721 has 8 divisors (see below), whose sum is σ = 28001382624. Its totient is φ = 13999900320.

The previous prime is 21000443719. The next prime is 21000443741. The reversal of 21000443721 is 12734400012.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21000443721 - 2¹ = 21000443719 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21000443691 and 21000443700.

It is not an unprimeable number, because it can be changed into a prime (21000443701) 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, 62781 + ... + 214341.

It is an arithmetic number, because the mean of its divisors is an integer number (3500172828).

Almost surely, 2^21000443721 is an apocalyptic number.

It is an amenable number.

21000443721 is a deficient number, since it is larger than the sum of its proper divisors (7000938903).

21000443721 is a wasteful number, since it uses less digits than its factorization.

21000443721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 197751.

The product of its (nonzero) digits is 1344, while the sum is 24.

Adding to 21000443721 its reverse (12734400012), we get a palindrome (33734843733).

The spelling of 21000443721 in words is "twenty-one billion, four hundred forty-three thousand, seven hundred twenty-one".