205871778869 has 2 divisors, whose sum is σ = 205871778870. Its totient is φ = 205871778868.

The previous prime is 205871778857. The next prime is 205871778899. The reversal of 205871778869 is 968877178502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 181045995025 + 24825783844 = 425495^2 + 157562^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-205871778869 is a prime.

It is a super-2 number, since 2×205871778869² (a number of 23 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 205871778799 and 205871778808.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (205871778809) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102935889434 + 102935889435.

It is an arithmetic number, because the mean of its divisors is an integer number (102935889435).

Almost surely, 2^205871778869 is an apocalyptic number.

It is an amenable number.

205871778869 is a deficient number, since it is larger than the sum of its proper divisors (1).

205871778869 is an equidigital number, since it uses as much as digits as its factorization.

205871778869 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 94832640, while the sum is 68.

The spelling of 205871778869 in words is "two hundred five billion, eight hundred seventy-one million, seven hundred seventy-eight thousand, eight hundred sixty-nine".