691217128057 has 2 divisors, whose sum is σ = 691217128058. Its totient is φ = 691217128056.

The previous prime is 691217128031. The next prime is 691217128061. The reversal of 691217128057 is 750821712196.

691217128057 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 can be written as a sum of positive squares in only one way, i.e., 654972964416 + 36244163641 = 809304^2 + 190379^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-691217128057 is a prime.

It is a super-2 number, since 2×691217128057² (a number of 24 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 691217128057.

It is not a weakly prime, because it can be changed into another prime (691217128097) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345608564028 + 345608564029.

It is an arithmetic number, because the mean of its divisors is an integer number (345608564029).

Almost surely, 2^691217128057 is an apocalyptic number.

It is an amenable number.

691217128057 is a deficient number, since it is larger than the sum of its proper divisors (1).

691217128057 is an equidigital number, since it uses as much as digits as its factorization.

691217128057 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 423360, while the sum is 49.

The spelling of 691217128057 in words is "six hundred ninety-one billion, two hundred seventeen million, one hundred twenty-eight thousand, fifty-seven".