691771032721 has 2 divisors, whose sum is σ = 691771032722. Its totient is φ = 691771032720.

The previous prime is 691771032709. The next prime is 691771032731. The reversal of 691771032721 is 127230177196.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 421902211600 + 269868821121 = 649540^2 + 519489^2 .

It is a cyclic number.

It is not a de Polignac number, because 691771032721 - 2¹⁷ = 691770901649 is a prime.

It is not a weakly prime, because it can be changed into another prime (691771032731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345885516360 + 345885516361.

It is an arithmetic number, because the mean of its divisors is an integer number (345885516361).

Almost surely, 2^691771032721 is an apocalyptic number.

It is an amenable number.

691771032721 is a deficient number, since it is larger than the sum of its proper divisors (1).

691771032721 is an equidigital number, since it uses as much as digits as its factorization.

691771032721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 222264, while the sum is 46.

The spelling of 691771032721 in words is "six hundred ninety-one billion, seven hundred seventy-one million, thirty-two thousand, seven hundred twenty-one".