21809440512 has 252 divisors, whose sum is σ = 68121933264. Its totient is φ = 6952366080.

The previous prime is 21809440501. The next prime is 21809440519. The reversal of 21809440512 is 21504490812.

21809440512 is a `hidden beast` number, since 2 + 18 + 0 + 94 + 40 + 512 = 666.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21809440519) by changing a digit.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 4289812 + ... + 4294892.

It is an arithmetic number, because the mean of its divisors is an integer number (270325132).

Almost surely, 2^21809440512 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 21809440512, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34060966632).

21809440512 is an abundant number, since it is smaller than the sum of its proper divisors (46312492752).

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

21809440512 is an frugal number, since it uses more digits than its factorization.

21809440512 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5138 (or 5109 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 36.

The spelling of 21809440512 in words is "twenty-one billion, eight hundred nine million, four hundred forty thousand, five hundred twelve".