331 has 2 divisors, whose sum is σ = 332. Its totient is φ = 330.

The previous prime is 317. The next prime is 337. The reversal of 331 is 133.

It is a happy number.

331 is nontrivially palindromic in base 15.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^{k}-331 is a prime.

It is a super-2 number, since 2×331^{2} = 219122, which contains 22 as substring.

331 is an undulating number in base 15.

331 is a lucky number.

It is a plaindrome in base 12, base 14 and base 16.

It is a nialpdrome in base 7 and base 10.

It is a panconsummate number.

It is not a weakly prime, because it can be changed into another prime (337) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 165 + 166.

It is an arithmetic number, because the mean of its divisors is an integer number (166).

331 is the 12-th centered pentagonal number and also the 11-th hex number.

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

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

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

The product of its digits is 9, while the sum is 7.

The square root of 331 is about 18.1934053987. The cubic root of 331 is about 6.9173964166.

The spelling of 331 in words is "three hundred thirty-one", and is thus an aban number.

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