• 12912 = 1666681 is the smallest square that contains exactly four digits '6'.
1291 has 2 divisors, whose sum is σ = 1292. Its totient is φ = 1290.
The previous prime is 1289. The next prime is 1297. The reversal of 1291 is 1921.
It is a weak prime.
It is a cyclic number.
It is not a de Polignac number, because 1291 - 21 = 1289 is a prime.
Together with 1289, it forms a pair of twin primes.
It is a Chen prime.
1291 is a lucky number.
It is a nialpdrome in base 6 and base 11.
It is a panconsummate number.
It is not a weakly prime, because it can be changed into another prime (1297) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (5) of ones.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 645 + 646.
It is an arithmetic number, because the mean of its divisors is an integer number (646).
1291 is a deficient number, since it is larger than the sum of its proper divisors (1).
1291 is an equidigital number, since it uses as much as digits as its factorization.
1291 is an odious number, because the sum of its binary digits is odd.
The product of its digits is 18, while the sum is 13.
The square root of 1291 is about 35.9304884464. The cubic root of 1291 is about 10.8886844949. Note that the first 3 decimals are identical.
Subtracting 1291 from its reverse (1921), we obtain a triangular number (630 = T35).
It can be divided in two parts, 1 and 291, that added together give a palindrome (292).
The spelling of 1291 in words is "one thousand, two hundred ninety-one".
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