205511531 has 2 divisors, whose sum is σ = 205511532. Its totient is φ = 205511530.

The previous prime is 205511513. The next prime is 205511533. The reversal of 205511531 is 135115502.

It is a happy number.

Together with previous prime (205511513) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 205511531 - 2²² = 201317227 is a prime.

It is a super-2 number, since 2×205511531² = 84469978747927922, which contains 22 as substring.

Together with 205511533, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 205511497 and 205511506.

It is not a weakly prime, because it can be changed into another prime (205511533) 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, 102755765 + 102755766.

It is an arithmetic number, because the mean of its divisors is an integer number (102755766).

Almost surely, 2^205511531 is an apocalyptic number.

205511531 is a deficient number, since it is larger than the sum of its proper divisors (1).

205511531 is an equidigital number, since it uses as much as digits as its factorization.

205511531 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 750, while the sum is 23.

The square root of 205511531 is about 14335.6733710001. The cubic root of 205511531 is about 590.1268816459.

The spelling of 205511531 in words is "two hundred five million, five hundred eleven thousand, five hundred thirty-one".