511991 has 2 divisors, whose sum is σ = 511992. Its totient is φ = 511990.

The previous prime is 511963. The next prime is 511997. The reversal of 511991 is 199115.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-511991 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 511991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (511997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 255995 + 255996.

It is an arithmetic number, because the mean of its divisors is an integer number (255996).

2⁵¹¹⁹⁹¹ is an apocalyptic number.

511991 is a deficient number, since it is larger than the sum of its proper divisors (1).

511991 is an equidigital number, since it uses as much as digits as its factorization.

511991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 405, while the sum is 26.

The square root of 511991 is about 715.5354638311. The cubic root of 511991 is about 79.9995312473. Note that the first 3 decimals are identical.

The spelling of 511991 in words is "five hundred eleven thousand, nine hundred ninety-one".