21008887649568 has 864 divisors, whose sum is σ = 77069314498176. Its totient is φ = 5512204099584.

The previous prime is 21008887649513. The next prime is 21008887649591. The reversal of 21008887649568 is 86594678880012.

21008887649568 is a `hidden beast` number, since 2 + 1 + 0 + 0 + 8 + 8 + 8 + 76 + 495 + 68 = 666.

It is a tau number, because it is divible by the number of its divisors (864).

It is a Harshad number since it is a multiple of its sum of digits (72).

It is a junction number, because it is equal to n+sod(n) for n = 21008887649496 and 21008887649505.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 1812198780 + ... + 1812210372.

It is an arithmetic number, because the mean of its divisors is an integer number (89200595484).

Almost surely, 2^{21008887649568} is an apocalyptic number.

21008887649568 is a gapful number since it is divisible by the number (28) 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 21008887649568, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38534657249088).

21008887649568 is an abundant number, since it is smaller than the sum of its proper divisors (56060426848608).

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

21008887649568 is a wasteful number, since it uses less digits than its factorization.

21008887649568 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11848 (or 11815 counting only the distinct ones).

The product of its (nonzero) digits is 371589120, while the sum is 72.

The spelling of 21008887649568 in words is "twenty-one trillion, eight billion, eight hundred eighty-seven million, six hundred forty-nine thousand, five hundred sixty-eight".