20905985880 has 384 divisors, whose sum is σ = 75549539520. Its totient is φ = 4981616640.

The previous prime is 20905985857. The next prime is 20905985899. The reversal of 20905985880 is 8858950902.

20905985880 is a `hidden beast` number, since 2 + 0 + 9 + 0 + 59 + 8 + 588 + 0 = 666.

It is a super-2 number, since 2×20905985880² (a number of 21 digits) contains 22 as substring.

It is a Smith number, since the sum of its digits (54) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 19126614 + ... + 19127706.

Almost surely, 2^20905985880 is an apocalyptic number.

20905985880 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 20905985880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37774769760).

20905985880 is an abundant number, since it is smaller than the sum of its proper divisors (54643553640).

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

20905985880 is a wasteful number, since it uses less digits than its factorization.

20905985880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1251 (or 1244 counting only the distinct ones).

The product of its (nonzero) digits is 2073600, while the sum is 54.

The spelling of 20905985880 in words is "twenty billion, nine hundred five million, nine hundred eighty-five thousand, eight hundred eighty".