205975981 has 2 divisors, whose sum is σ = 205975982. Its totient is φ = 205975980.

The previous prime is 205975933. The next prime is 205976027. The reversal of 205975981 is 189579502.

It is an a-pointer prime, because the next prime (205976027) can be obtained adding 205975981 to its sum of digits (46).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 203319081 + 2656900 = 14259^2 + 1630^2 .

It is a cyclic number.

It is not a de Polignac number, because 205975981 - 2¹⁷ = 205844909 is a prime.

It is a super-2 number, since 2×205975981² = 84852209497824722, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (205975901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102987990 + 102987991.

It is an arithmetic number, because the mean of its divisors is an integer number (102987991).

Almost surely, 2^205975981 is an apocalyptic number.

It is an amenable number.

205975981 is a deficient number, since it is larger than the sum of its proper divisors (1).

205975981 is an equidigital number, since it uses as much as digits as its factorization.

205975981 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 square root of 205975981 is about 14351.8633285020. The cubic root of 205975981 is about 590.5711036213.

The spelling of 205975981 in words is "two hundred five million, nine hundred seventy-five thousand, nine hundred eighty-one".