21681418381560 has 768 divisors, whose sum is σ = 85191575040000. Its totient is φ = 4671610785792.

The previous prime is 21681418381523. The next prime is 21681418381573. The reversal of 21681418381560 is 6518381418612.

21681418381560 is a `hidden beast` number, since 2 + 1 + 6 + 8 + 1 + 41 + 8 + 38 + 1 + 560 = 666.

It is a Cunningham number, because it is equal to 4656331²-1.

It is a junction number, because it is equal to n+sod(n) for n = 21681418381497 and 21681418381506.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 9480286737 + ... + 9480289023.

It is an arithmetic number, because the mean of its divisors is an integer number (110926530000).

Almost surely, 2^{21681418381560} is an apocalyptic number.

21681418381560 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 21681418381560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42595787520000).

21681418381560 is an abundant number, since it is smaller than the sum of its proper divisors (63510156658440).

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

21681418381560 is a wasteful number, since it uses less digits than its factorization.

21681418381560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3228 (or 3221 counting only the distinct ones).

The product of its (nonzero) digits is 2211840, while the sum is 54.

The spelling of 21681418381560 in words is "twenty-one trillion, six hundred eighty-one billion, four hundred eighteen million, three hundred eighty-one thousand, five hundred sixty".