21166568640 has 336 divisors, whose sum is σ = 83716319232. Its totient is φ = 4808337408.

The previous prime is 21166568629. The next prime is 21166568663. The reversal of 21166568640 is 4686566112.

21166568640 is a `hidden beast` number, since 21 + 1 + 6 + 6 + 568 + 64 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (336).

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

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, 3363577 + ... + 3369863.

It is an arithmetic number, because the mean of its divisors is an integer number (249155712).

Almost surely, 2^21166568640 is an apocalyptic number.

21166568640 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 21166568640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41858159616).

21166568640 is an abundant number, since it is smaller than the sum of its proper divisors (62549750592).

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

21166568640 is a wasteful number, since it uses less digits than its factorization.

21166568640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6484 (or 6471 counting only the distinct ones).

The product of its (nonzero) digits is 414720, while the sum is 45.

It can be divided in two parts, 2116 and 6568640, that added together give a palindrome (6570756).

The spelling of 21166568640 in words is "twenty-one billion, one hundred sixty-six million, five hundred sixty-eight thousand, six hundred forty".