20509019857 has 2 divisors, whose sum is σ = 20509019858. Its totient is φ = 20509019856.

The previous prime is 20509019837. The next prime is 20509019887. The reversal of 20509019857 is 75891090502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18324766161 + 2184253696 = 135369^2 + 46736^2 .

It is a cyclic number.

It is not a de Polignac number, because 20509019857 - 2¹⁵ = 20508987089 is a prime.

It is not a weakly prime, because it can be changed into another prime (20509019837) 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, 10254509928 + 10254509929.

It is an arithmetic number, because the mean of its divisors is an integer number (10254509929).

Almost surely, 2^20509019857 is an apocalyptic number.

It is an amenable number.

20509019857 is a deficient number, since it is larger than the sum of its proper divisors (1).

20509019857 is an equidigital number, since it uses as much as digits as its factorization.

20509019857 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 226800, while the sum is 46.

The spelling of 20509019857 in words is "twenty billion, five hundred nine million, nineteen thousand, eight hundred fifty-seven".