20809635840 has 288 divisors, whose sum is σ = 82428222240. Its totient is φ = 4756340736.

The previous prime is 20809635827. The next prime is 20809635853. The reversal of 20809635840 is 4853690802.

20809635840 is a `hidden beast` number, since 2 + 0 + 8 + 0 + 9 + 63 + 584 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (20809635827) and next prime (20809635853).

It is a tau number, because it is divible by the number of its divisors (288).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 628992 + ... + 661248.

It is an arithmetic number, because the mean of its divisors is an integer number (286209105).

Almost surely, 2^20809635840 is an apocalyptic number.

20809635840 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 20809635840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41214111120).

20809635840 is an abundant number, since it is smaller than the sum of its proper divisors (61618586400).

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

20809635840 is a wasteful number, since it uses less digits than its factorization.

20809635840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32297 (or 32274 counting only the distinct ones).

The product of its (nonzero) digits is 414720, while the sum is 45.

The spelling of 20809635840 in words is "twenty billion, eight hundred nine million, six hundred thirty-five thousand, eight hundred forty".