20809700640 has 288 divisors, whose sum is σ = 72176832000. Its totient is φ = 5459097600.

The previous prime is 20809700609. The next prime is 20809700647. The reversal of 20809700640 is 4600790802.

20809700640 is a `hidden beast` number, since 2 + 0 + 8 + 0 + 9 + 7 + 0 + 0 + 640 = 666.

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 (36).

It is a junction number, because it is equal to n+sod(n) for n = 20809700595 and 20809700604.

It is not an unprimeable number, because it can be changed into a prime (20809700647) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 28942201 + ... + 28942919.

It is an arithmetic number, because the mean of its divisors is an integer number (250614000).

Almost surely, 2^20809700640 is an apocalyptic number.

20809700640 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 20809700640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36088416000).

20809700640 is an abundant number, since it is smaller than the sum of its proper divisors (51367131360).

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

20809700640 is a wasteful number, since it uses less digits than its factorization.

20809700640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1040 (or 1029 counting only the distinct ones).

The product of its (nonzero) digits is 24192, while the sum is 36.

The spelling of 20809700640 in words is "twenty billion, eight hundred nine million, seven hundred thousand, six hundred forty".