20781556992 has 540 divisors, whose sum is σ = 73123566516. Its totient is φ = 5852528640.

The previous prime is 20781556979. The next prime is 20781557009. The reversal of 20781556992 is 29965518702.

20781556992 is a `hidden beast` number, since 2 + 0 + 7 + 81 + 556 + 9 + 9 + 2 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 293642496 + 20487914496 = 17136^2 + 143136^2 .

It is a super-2 number, since 2×20781556992² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 114815142 + ... + 114815322.

Almost surely, 2^20781556992 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20781556992, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36561783258).

20781556992 is an abundant number, since it is smaller than the sum of its proper divisors (52342009524).

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

20781556992 is a wasteful number, since it uses less digits than its factorization.

20781556992 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 336 (or 306 counting only the distinct ones).

The product of its (nonzero) digits is 2721600, while the sum is 54.

The spelling of 20781556992 in words is "twenty billion, seven hundred eighty-one million, five hundred fifty-six thousand, nine hundred ninety-two".