691055857 has 2 divisors, whose sum is σ = 691055858. Its totient is φ = 691055856.

The previous prime is 691055809. The next prime is 691055863. The reversal of 691055857 is 758550196.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 493906176 + 197149681 = 22224^2 + 14041^2 .

It is a cyclic number.

It is not a de Polignac number, because 691055857 - 2²⁷ = 556838129 is a prime.

It is not a weakly prime, because it can be changed into another prime (691056857) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345527928 + 345527929.

It is an arithmetic number, because the mean of its divisors is an integer number (345527929).

Almost surely, 2^691055857 is an apocalyptic number.

It is an amenable number.

691055857 is a deficient number, since it is larger than the sum of its proper divisors (1).

691055857 is an equidigital number, since it uses as much as digits as its factorization.

691055857 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 378000, while the sum is 46.

The square root of 691055857 is about 26287.9412849314. The cubic root of 691055857 is about 884.1060939017.

The spelling of 691055857 in words is "six hundred ninety-one million, fifty-five thousand, eight hundred fifty-seven".