21006440928 has 288 divisors, whose sum is σ = 67705878240. Its totient is φ = 6119608320.

The previous prime is 21006440927. The next prime is 21006440947. The reversal of 21006440928 is 82904460012.

21006440928 is a `hidden beast` number, since 2 + 1 + 0 + 0 + 644 + 0 + 9 + 2 + 8 = 666.

It is a tau number, because it is divible by the number of its divisors (288).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21006440892 and 21006440901.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21006440927) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 34267950 + ... + 34268562.

It is an arithmetic number, because the mean of its divisors is an integer number (235089855).

Almost surely, 2^21006440928 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21006440928, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33852939120).

21006440928 is an abundant number, since it is smaller than the sum of its proper divisors (46699437312).

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

21006440928 is a wasteful number, since it uses less digits than its factorization.

21006440928 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1042 (or 1031 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 36.

The spelling of 21006440928 in words is "twenty-one billion, six million, four hundred forty thousand, nine hundred twenty-eight".