21709642064 has 80 divisors (see below), whose sum is σ = 47064737664. Its totient is φ = 9617088000.

The previous prime is 21709642037. The next prime is 21709642069. The reversal of 21709642064 is 46024690712.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21709642069) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1400822 + ... + 1416234.

Almost surely, 2^21709642064 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 21709642064, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23532368832).

21709642064 is an abundant number, since it is smaller than the sum of its proper divisors (25355095600).

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

21709642064 is a wasteful number, since it uses less digits than its factorization.

21709642064 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15636 (or 15630 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 41.

The spelling of 21709642064 in words is "twenty-one billion, seven hundred nine million, six hundred forty-two thousand, sixty-four".