21701920660 has 72 divisors (see below), whose sum is σ = 53401990824. Its totient is φ = 7386301440.

The previous prime is 21701920657. The next prime is 21701920693. The reversal of 21701920660 is 6602910712.

It can be written as a sum of positive squares in 4 ways, for example, as 1858127236 + 19843793424 = 43106^2 + 140868^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 53440 + ... + 215080.

It is an arithmetic number, because the mean of its divisors is an integer number (741694317).

Almost surely, 2^21701920660 is an apocalyptic number.

21701920660 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 21701920660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26700995412).

21701920660 is an abundant number, since it is smaller than the sum of its proper divisors (31700070164).

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

21701920660 is a wasteful number, since it uses less digits than its factorization.

21701920660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 161801 (or 161792 counting only the distinct ones).

The product of its (nonzero) digits is 9072, while the sum is 34.

The spelling of 21701920660 in words is "twenty-one billion, seven hundred one million, nine hundred twenty thousand, six hundred sixty".