691813 has 2 divisors, whose sum is σ = 691814. Its totient is φ = 691812.

The previous prime is 691799. The next prime is 691829. The reversal of 691813 is 318196.

It is a happy number.

691813 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 can be written as a sum of positive squares in only one way, i.e., 675684 + 16129 = 822^2 + 127^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-691813 is a prime.

It is an Ulam number.

It is equal to p₅₅₉₃₆ and since 691813 and 55936 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (691843) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345906 + 345907.

It is an arithmetic number, because the mean of its divisors is an integer number (345907).

2⁶⁹¹⁸¹³ is an apocalyptic number.

It is an amenable number.

691813 is a deficient number, since it is larger than the sum of its proper divisors (1).

691813 is an equidigital number, since it uses as much as digits as its factorization.

691813 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1296, while the sum is 28.

The square root of 691813 is about 831.7529681342. The cubic root of 691813 is about 88.4428861066.

It can be divided in two parts, 6 and 91813, that added together give a palindrome (91819).

The spelling of 691813 in words is "six hundred ninety-one thousand, eight hundred thirteen".