20815280640 has 640 divisors, whose sum is σ = 92205527040. Its totient is φ = 4324147200.

The previous prime is 20815280639. The next prime is 20815280659. The reversal of 20815280640 is 4608251802.

20815280640 is a `hidden beast` number, since 2 + 0 + 8 + 1 + 5 + 2 + 8 + 0 + 640 = 666.

It is a tau number, because it is divible by the number of its divisors (640).

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 = 20815280595 and 20815280604.

It is a congruent number.

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 63 ways as a sum of consecutive naturals, for example, 5320285 + ... + 5324195.

It is an arithmetic number, because the mean of its divisors is an integer number (144071136).

Almost surely, 2^20815280640 is an apocalyptic number.

20815280640 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 20815280640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (46102763520).

20815280640 is an abundant number, since it is smaller than the sum of its proper divisors (71390246400).

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

20815280640 is a wasteful number, since it uses less digits than its factorization.

20815280640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3961 (or 3939 counting only the distinct ones).

The product of its (nonzero) digits is 30720, while the sum is 36.

The spelling of 20815280640 in words is "twenty billion, eight hundred fifteen million, two hundred eighty thousand, six hundred forty".