21666064420 has 576 divisors, whose sum is σ = 66924748800. Its totient is φ = 5774146560.

The previous prime is 21666064417. The next prime is 21666064447. The reversal of 21666064420 is 2446066612.

It is a self number, because there is not a number n which added to its sum of digits gives 21666064420.

It is an unprimeable number.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 210350089 + ... + 210350191.

It is an arithmetic number, because the mean of its divisors is an integer number (116188800).

Almost surely, 2^21666064420 is an apocalyptic number.

21666064420 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 21666064420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33462374400).

21666064420 is an abundant number, since it is smaller than the sum of its proper divisors (45258684380).

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

21666064420 is a wasteful number, since it uses less digits than its factorization.

21666064420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 248 (or 239 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 37.

The spelling of 21666064420 in words is "twenty-one billion, six hundred sixty-six million, sixty-four thousand, four hundred twenty".