20509019856 has 100 divisors (see below), whose sum is σ = 63925187172. Its totient is φ = 6310462464.

The previous prime is 20509019837. The next prime is 20509019857. The reversal of 20509019856 is 65891090502.

20509019856 is a `hidden beast` number, since 2 + 0 + 509 + 0 + 1 + 98 + 56 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 5580090000 + 14928929856 = 74700^2 + 122184^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20509019857) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 591801 + ... + 625496.

Almost surely, 2^20509019856 is an apocalyptic number.

20509019856 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

20509019856 is an abundant number, since it is smaller than the sum of its proper divisors (43416167316).

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

20509019856 is a wasteful number, since it uses less digits than its factorization.

20509019856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1217330 (or 1217315 counting only the distinct ones).

The product of its (nonzero) digits is 194400, while the sum is 45.

The spelling of 20509019856 in words is "twenty billion, five hundred nine million, nineteen thousand, eight hundred fifty-six".