691340257 has 2 divisors, whose sum is σ = 691340258. Its totient is φ = 691340256.

The previous prime is 691340231. The next prime is 691340261. The reversal of 691340257 is 752043196.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 417139776 + 274200481 = 20424^2 + 16559^2 .

It is a cyclic number.

It is not a de Polignac number, because 691340257 - 2²⁷ = 557122529 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (691340057) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345670128 + 345670129.

It is an arithmetic number, because the mean of its divisors is an integer number (345670129).

Almost surely, 2^691340257 is an apocalyptic number.

It is an amenable number.

691340257 is a deficient number, since it is larger than the sum of its proper divisors (1).

691340257 is an equidigital number, since it uses as much as digits as its factorization.

691340257 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 45360, while the sum is 37.

The square root of 691340257 is about 26293.3500528175. The cubic root of 691340257 is about 884.2273601667.

The spelling of 691340257 in words is "six hundred ninety-one million, three hundred forty thousand, two hundred fifty-seven".