691591 has 2 divisors, whose sum is σ = 691592. Its totient is φ = 691590.

The previous prime is 691589. The next prime is 691631. The reversal of 691591 is 195196.

691591 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 691591 - 2¹ = 691589 is a prime.

It is a super-2 number, since 2×691591² = 956596222562, which contains 22 as substring.

Together with 691589, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (691531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345795 + 345796.

It is an arithmetic number, because the mean of its divisors is an integer number (345796).

2⁶⁹¹⁵⁹¹ is an apocalyptic number.

691591 is a deficient number, since it is larger than the sum of its proper divisors (1).

691591 is an equidigital number, since it uses as much as digits as its factorization.

691591 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2430, while the sum is 31.

The square root of 691591 is about 831.6195043408. The cubic root of 691591 is about 88.4334247728.

The spelling of 691591 in words is "six hundred ninety-one thousand, five hundred ninety-one".