205756981 has 2 divisors, whose sum is σ = 205756982. Its totient is φ = 205756980.

The previous prime is 205756961. The next prime is 205757017. The reversal of 205756981 is 189657502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 197543025 + 8213956 = 14055^2 + 2866^2 .

It is a cyclic number.

It is not a de Polignac number, because 205756981 - 2¹³ = 205748789 is a prime.

It is a super-2 number, since 2×205756981² = 84671870460468722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (205756921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102878490 + 102878491.

It is an arithmetic number, because the mean of its divisors is an integer number (102878491).

Almost surely, 2^205756981 is an apocalyptic number.

It is an amenable number.

205756981 is a deficient number, since it is larger than the sum of its proper divisors (1).

205756981 is an equidigital number, since it uses as much as digits as its factorization.

205756981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 151200, while the sum is 43.

The square root of 205756981 is about 14344.2316280796. The cubic root of 205756981 is about 590.3617249422.

It can be divided in two parts, 20575 and 6981, that added together give a square (27556 = 166²).

The spelling of 205756981 in words is "two hundred five million, seven hundred fifty-six thousand, nine hundred eighty-one".