20509817904 has 120 divisors (see below), whose sum is σ = 58080804912. Its totient is φ = 6755673600.

The previous prime is 20509817893. The next prime is 20509817921. The reversal of 20509817904 is 40971890502.

It is a self number, because there is not a number n which added to its sum of digits gives 20509817904.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 9845247 + ... + 9847329.

Almost surely, 2^20509817904 is an apocalyptic number.

20509817904 is a gapful number since it is divisible by the number (24) 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 20509817904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29040402456).

20509817904 is an abundant number, since it is smaller than the sum of its proper divisors (37570987008).

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

20509817904 is a wasteful number, since it uses less digits than its factorization.

20509817904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2875 (or 2866 counting only the distinct ones).

The product of its (nonzero) digits is 181440, while the sum is 45.

The spelling of 20509817904 in words is "twenty billion, five hundred nine million, eight hundred seventeen thousand, nine hundred four".