20981321677 has 2 divisors, whose sum is σ = 20981321678. Its totient is φ = 20981321676.

The previous prime is 20981321567. The next prime is 20981321693. The reversal of 20981321677 is 77612318902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15561564516 + 5419757161 = 124746^2 + 73619^2 .

It is a cyclic number.

It is not a de Polignac number, because 20981321677 - 2¹¹ = 20981319629 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20981321077) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10490660838 + 10490660839.

It is an arithmetic number, because the mean of its divisors is an integer number (10490660839).

Almost surely, 2^20981321677 is an apocalyptic number.

It is an amenable number.

20981321677 is a deficient number, since it is larger than the sum of its proper divisors (1).

20981321677 is an equidigital number, since it uses as much as digits as its factorization.

20981321677 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 254016, while the sum is 46.

The spelling of 20981321677 in words is "twenty billion, nine hundred eighty-one million, three hundred twenty-one thousand, six hundred seventy-seven".