691275391 has 2 divisors, whose sum is σ = 691275392. Its totient is φ = 691275390.

The previous prime is 691275379. The next prime is 691275397. The reversal of 691275391 is 193572196.

691275391 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 691275391 - 2¹⁵ = 691242623 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (691275397) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345637695 + 345637696.

It is an arithmetic number, because the mean of its divisors is an integer number (345637696).

Almost surely, 2^691275391 is an apocalyptic number.

691275391 is a deficient number, since it is larger than the sum of its proper divisors (1).

691275391 is an equidigital number, since it uses as much as digits as its factorization.

691275391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 102060, while the sum is 43.

The square root of 691275391 is about 26292.1165180744. The cubic root of 691275391 is about 884.1997046646.

The spelling of 691275391 in words is "six hundred ninety-one million, two hundred seventy-five thousand, three hundred ninety-one".