20431805981 has 2 divisors, whose sum is σ = 20431805982. Its totient is φ = 20431805980.

The previous prime is 20431805959. The next prime is 20431805987. The reversal of 20431805981 is 18950813402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11830912900 + 8600893081 = 108770^2 + 92741^2 .

It is a cyclic number.

It is not a de Polignac number, because 20431805981 - 2¹⁰ = 20431804957 is a prime.

It is a super-2 number, since 2×20431805981² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20431805987) 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 as a sum of consecutive naturals, namely, 10215902990 + 10215902991.

It is an arithmetic number, because the mean of its divisors is an integer number (10215902991).

Almost surely, 2^20431805981 is an apocalyptic number.

It is an amenable number.

20431805981 is a deficient number, since it is larger than the sum of its proper divisors (1).

20431805981 is an equidigital number, since it uses as much as digits as its factorization.

20431805981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 69120, while the sum is 41.

The spelling of 20431805981 in words is "twenty billion, four hundred thirty-one million, eight hundred five thousand, nine hundred eighty-one".