21017709680 has 240 divisors, whose sum is σ = 55592816832. Its totient is φ = 7380172800.

The previous prime is 21017709677. The next prime is 21017709697. The reversal of 21017709680 is 8690771012.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 36425552 + ... + 36426128.

Almost surely, 2^21017709680 is an apocalyptic number.

21017709680 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 21017709680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27796408416).

21017709680 is an abundant number, since it is smaller than the sum of its proper divisors (34575107152).

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

21017709680 is a wasteful number, since it uses less digits than its factorization.

21017709680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 736 (or 719 counting only the distinct ones).

The product of its (nonzero) digits is 42336, while the sum is 41.

The spelling of 21017709680 in words is "twenty-one billion, seventeen million, seven hundred nine thousand, six hundred eighty".