691581257 has 2 divisors, whose sum is σ = 691581258. Its totient is φ = 691581256.

The previous prime is 691581229. The next prime is 691581269. The reversal of 691581257 is 752185196.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 687435961 + 4145296 = 26219^2 + 2036^2 .

It is a cyclic number.

It is not a de Polignac number, because 691581257 - 2⁸ = 691581001 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (691581277) 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, 345790628 + 345790629.

It is an arithmetic number, because the mean of its divisors is an integer number (345790629).

Almost surely, 2^691581257 is an apocalyptic number.

It is an amenable number.

691581257 is a deficient number, since it is larger than the sum of its proper divisors (1).

691581257 is an equidigital number, since it uses as much as digits as its factorization.

691581257 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 151200, while the sum is 44.

The square root of 691581257 is about 26297.9325613250. The cubic root of 691581257 is about 884.3300949318.

The spelling of 691581257 in words is "six hundred ninety-one million, five hundred eighty-one thousand, two hundred fifty-seven".