21487616561664 has 1920 divisors, whose sum is σ = 77236270848000. Its totient is φ = 5831626752000.

The previous prime is 21487616561657. The next prime is 21487616561669. The reversal of 21487616561664 is 46616561678412.

21487616561664 is a `hidden beast` number, since 2 + 1 + 4 + 8 + 7 + 6 + 1 + 6 + 5 + 616 + 6 + 4 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21487616561669) by changing a digit.

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 191 ways as a sum of consecutive naturals, for example, 197134096842 + ... + 197134096950.

It is an arithmetic number, because the mean of its divisors is an integer number (40227224400).

Almost surely, 2^{21487616561664} is an apocalyptic number.

21487616561664 is a gapful number since it is divisible by the number (24) 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 21487616561664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38618135424000).

21487616561664 is an abundant number, since it is smaller than the sum of its proper divisors (55748654286336).

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

21487616561664 is a wasteful number, since it uses less digits than its factorization.

21487616561664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 299 (or 246 counting only the distinct ones).

The product of its digits is 69672960, while the sum is 63.

The spelling of 21487616561664 in words is "twenty-one trillion, four hundred eighty-seven billion, six hundred sixteen million, five hundred sixty-one thousand, six hundred sixty-four".