21709441920 has 128 divisors (see below), whose sum is σ = 69240407040. Its totient is φ = 5785708544.

The previous prime is 21709441891. The next prime is 21709441921. The reversal of 21709441920 is 2914490712.

It is a tau number, because it is divible by the number of its divisors (128).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21709441921) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5617909 + ... + 5621771.

It is an arithmetic number, because the mean of its divisors is an integer number (540940680).

Almost surely, 2^21709441920 is an apocalyptic number.

21709441920 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 21709441920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34620203520).

21709441920 is an abundant number, since it is smaller than the sum of its proper divisors (47530965120).

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

21709441920 is a wasteful number, since it uses less digits than its factorization.

21709441920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6812 (or 6800 counting only the distinct ones).

The product of its (nonzero) digits is 36288, while the sum is 39.

The spelling of 21709441920 in words is "twenty-one billion, seven hundred nine million, four hundred forty-one thousand, nine hundred twenty".