21785819520 has 256 divisors, whose sum is σ = 73488960000. Its totient is φ = 5474304000.

The previous prime is 21785819509. The next prime is 21785819537. The reversal of 21785819520 is 2591858712.

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a self number, because there is not a number n which added to its sum of digits gives 21785819520.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 7258020 + ... + 7261020.

It is an arithmetic number, because the mean of its divisors is an integer number (287066250).

Almost surely, 2^21785819520 is an apocalyptic number.

21785819520 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 21785819520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36744480000).

21785819520 is an abundant number, since it is smaller than the sum of its proper divisors (51703140480).

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

21785819520 is a wasteful number, since it uses less digits than its factorization.

21785819520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3241 (or 3229 counting only the distinct ones).

The product of its (nonzero) digits is 403200, while the sum is 48.

The spelling of 21785819520 in words is "twenty-one billion, seven hundred eighty-five million, eight hundred nineteen thousand, five hundred twenty".