20781568772640 has 1440 divisors, whose sum is σ = 86146135857936. Its totient is φ = 4696780308480.

The previous prime is 20781568772639. The next prime is 20781568772669. The reversal of 20781568772640 is 4627786518702.

It is a happy number.

20781568772640 is a `hidden beast` number, since 2 + 0 + 7 + 8 + 1 + 568 + 7 + 7 + 2 + 64 + 0 = 666.

It can be written as a sum of positive squares in 24 ways, for example, as 14381903353104 + 6399665419536 = 3792348^2 + 2529756^2 .

It is a tau number, because it is divible by the number of its divisors (1440).

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 239 ways as a sum of consecutive naturals, for example, 1526590474 + ... + 1526604086.

Almost surely, 2^{20781568772640} is an apocalyptic number.

20781568772640 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 20781568772640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43073067928968).

20781568772640 is an abundant number, since it is smaller than the sum of its proper divisors (65364567085296).

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

20781568772640 is a wasteful number, since it uses less digits than its factorization.

20781568772640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13724 (or 13694 counting only the distinct ones).

The product of its (nonzero) digits is 63221760, while the sum is 63.

The spelling of 20781568772640 in words is "twenty trillion, seven hundred eighty-one billion, five hundred sixty-eight million, seven hundred seventy-two thousand, six hundred forty".