21605179680 has 768 divisors, whose sum is σ = 93981081600. Its totient is φ = 4523765760.

The previous prime is 21605179639. The next prime is 21605179693. The reversal of 21605179680 is 8697150612.

21605179680 is a `hidden beast` number, since 21 + 605 + 17 + 9 + 6 + 8 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 17810754 + ... + 17811966.

It is an arithmetic number, because the mean of its divisors is an integer number (122371200).

Almost surely, 2^21605179680 is an apocalyptic number.

21605179680 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 21605179680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (46990540800).

21605179680 is an abundant number, since it is smaller than the sum of its proper divisors (72375901920).

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

21605179680 is a wasteful number, since it uses less digits than its factorization.

21605179680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1294 (or 1280 counting only the distinct ones).

The product of its (nonzero) digits is 181440, while the sum is 45.

The spelling of 21605179680 in words is "twenty-one billion, six hundred five million, one hundred seventy-nine thousand, six hundred eighty".