21809707920 has 1440 divisors, whose sum is σ = 104232078720. Its totient is φ = 4151347200.

The previous prime is 21809707879. The next prime is 21809707957. The reversal of 21809707920 is 2970790812.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

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 287 ways as a sum of consecutive naturals, for example, 166486255 + ... + 166486385.

It is an arithmetic number, because the mean of its divisors is an integer number (72383388).

Almost surely, 2^21809707920 is an apocalyptic number.

21809707920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21809707920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (52116039360).

21809707920 is an abundant number, since it is smaller than the sum of its proper divisors (82422370800).

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

21809707920 is a wasteful number, since it uses less digits than its factorization.

21809707920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 202 (or 172 counting only the distinct ones).

The product of its (nonzero) digits is 127008, while the sum is 45.

The spelling of 21809707920 in words is "twenty-one billion, eight hundred nine million, seven hundred seven thousand, nine hundred twenty".