20981778168 has 128 divisors (see below), whose sum is σ = 58603406400. Its totient is φ = 6215602176.

The previous prime is 20981778163. The next prime is 20981778173. The reversal of 20981778168 is 86187718902.

It is an interprime number because it is at equal distance from previous prime (20981778163) and next prime (20981778173).

It is a super-2 number, since 2×20981778168² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20981778161) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 3371796 + ... + 3378012.

Almost surely, 2^20981778168 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20981778168, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29301703200).

20981778168 is an abundant number, since it is smaller than the sum of its proper divisors (37621628232).

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

20981778168 is a wasteful number, since it uses less digits than its factorization.

20981778168 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6641 (or 6637 counting only the distinct ones).

The product of its (nonzero) digits is 2709504, while the sum is 57.

The spelling of 20981778168 in words is "twenty billion, nine hundred eighty-one million, seven hundred seventy-eight thousand, one hundred sixty-eight".