691181 has 2 divisors, whose sum is σ = 691182. Its totient is φ = 691180.

The previous prime is 691153. The next prime is 691183. The reversal of 691181 is 181196.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 624100 + 67081 = 790^2 + 259^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-691181 is a prime.

It is a super-3 number, since 3×691181³ = 990596133307448223, which contains 333 as substring. Note that it is a super-d number also for d = 2.

Together with 691183, it forms a pair of twin primes.

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 691181.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (691183) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345590 + 345591.

It is an arithmetic number, because the mean of its divisors is an integer number (345591).

2⁶⁹¹¹⁸¹ is an apocalyptic number.

It is an amenable number.

691181 is a deficient number, since it is larger than the sum of its proper divisors (1).

691181 is an equidigital number, since it uses as much as digits as its factorization.

691181 is an evil number, because the sum of its binary digits is even.

The product of its digits is 432, while the sum is 26.

The square root of 691181 is about 831.3729608305. The cubic root of 691181 is about 88.4159458141.

The spelling of 691181 in words is "six hundred ninety-one thousand, one hundred eighty-one".