20981321568 has 96 divisors (see below), whose sum is σ = 61248337920. Its totient is φ = 6987738240.

The previous prime is 20981321567. The next prime is 20981321677. The reversal of 20981321568 is 86512318902.

20981321568 is a `hidden beast` number, since 2 + 0 + 9 + 81 + 3 + 2 + 1 + 568 = 666.

It is a tau number, because it is divible by the number of its divisors (96).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20981321567) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1053721 + ... + 1073447.

It is an arithmetic number, because the mean of its divisors is an integer number (638003520).

Almost surely, 2^20981321568 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 20981321568, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30624168960).

20981321568 is an abundant number, since it is smaller than the sum of its proper divisors (40267016352).

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

20981321568 is a wasteful number, since it uses less digits than its factorization.

20981321568 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20977 (or 20963 counting only the distinct ones).

The product of its (nonzero) digits is 207360, while the sum is 45.

The spelling of 20981321568 in words is "twenty billion, nine hundred eighty-one million, three hundred twenty-one thousand, five hundred sixty-eight".