20511681840 has 400 divisors, whose sum is σ = 81238737888. Its totient is φ = 4751695872.

The previous prime is 20511681811. The next prime is 20511681893. The reversal of 20511681840 is 4818611502.

20511681840 is a `hidden beast` number, since 2 + 0 + 511 + 68 + 1 + 84 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 20511681795 and 20511681804.

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 79 ways as a sum of consecutive naturals, for example, 1424919 + ... + 1439241.

Almost surely, 2^20511681840 is an apocalyptic number.

20511681840 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 20511681840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40619368944).

20511681840 is an abundant number, since it is smaller than the sum of its proper divisors (60727056048).

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

20511681840 is a wasteful number, since it uses less digits than its factorization.

20511681840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14378 (or 14363 counting only the distinct ones).

The product of its (nonzero) digits is 15360, while the sum is 36.

The spelling of 20511681840 in words is "twenty billion, five hundred eleven million, six hundred eighty-one thousand, eight hundred forty".