21205473728 has 56 divisors (see below), whose sum is σ = 43648762080. Its totient is φ = 10209346560.

The previous prime is 21205473713. The next prime is 21205473739. The reversal of 21205473728 is 82737450212.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 676973 + ... + 707603.

It is an arithmetic number, because the mean of its divisors is an integer number (779442180).

Almost surely, 2^21205473728 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 21205473728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21824381040).

21205473728 is an abundant number, since it is smaller than the sum of its proper divisors (22443288352).

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

21205473728 is a wasteful number, since it uses less digits than its factorization.

21205473728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31045 (or 31035 counting only the distinct ones).

The product of its (nonzero) digits is 188160, while the sum is 41.

The spelling of 21205473728 in words is "twenty-one billion, two hundred five million, four hundred seventy-three thousand, seven hundred twenty-eight".