21389721760 has 144 divisors (see below), whose sum is σ = 55656937728. Its totient is φ = 7762388480.

The previous prime is 21389721739. The next prime is 21389721767. The reversal of 21389721760 is 6712798312.

It is a self number, because there is not a number n which added to its sum of digits gives 21389721760.

It is not an unprimeable number, because it can be changed into a prime (21389721767) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 14383737 + ... + 14385223.

It is an arithmetic number, because the mean of its divisors is an integer number (386506512).

Almost surely, 2^21389721760 is an apocalyptic number.

21389721760 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 21389721760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27828468864).

21389721760 is an abundant number, since it is smaller than the sum of its proper divisors (34267215968).

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

21389721760 is a wasteful number, since it uses less digits than its factorization.

21389721760 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2267 (or 2248 counting only the distinct ones).

The product of its (nonzero) digits is 254016, while the sum is 46.

The spelling of 21389721760 in words is "twenty-one billion, three hundred eighty-nine million, seven hundred twenty-one thousand, seven hundred sixty".