511681 has 4 divisors (see below), whose sum is σ = 533952. Its totient is φ = 489412.

The previous prime is 511669. The next prime is 511691. The reversal of 511681 is 186115.

511681 is nontrivially palindromic in base 5.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 186115 = 5 ⋅37223.

It is a cyclic number.

It is not a de Polignac number, because 511681 - 2⁹ = 511169 is a prime.

It is a super-2 number, since 2×511681² = 523634891522, which contains 22 as substring.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (511631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11101 + ... + 11146.

It is an arithmetic number, because the mean of its divisors is an integer number (133488).

2⁵¹¹⁶⁸¹ is an apocalyptic number.

It is an amenable number.

511681 is a deficient number, since it is larger than the sum of its proper divisors (22271).

511681 is a wasteful number, since it uses less digits than its factorization.

511681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22270.

The product of its digits is 240, while the sum is 22.

The square root of 511681 is about 715.3188100421. The cubic root of 511681 is about 79.9833819649.

Adding to 511681 its reverse (186115), we get a palindrome (697796).

The spelling of 511681 in words is "five hundred eleven thousand, six hundred eighty-one".