21684729648 has 80 divisors (see below), whose sum is σ = 57924864000. Its totient is φ = 6983109120.

The previous prime is 21684729589. The next prime is 21684729673. The reversal of 21684729648 is 84692748612.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 879148 + ... + 903476.

It is an arithmetic number, because the mean of its divisors is an integer number (724060800).

Almost surely, 2^21684729648 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 21684729648, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28962432000).

21684729648 is an abundant number, since it is smaller than the sum of its proper divisors (36240134352).

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

21684729648 is a wasteful number, since it uses less digits than its factorization.

21684729648 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24970 (or 24964 counting only the distinct ones).

The product of its digits is 9289728, while the sum is 57.

The spelling of 21684729648 in words is "twenty-one billion, six hundred eighty-four million, seven hundred twenty-nine thousand, six hundred forty-eight".