691665687607 has 4 divisors (see below), whose sum is σ = 707750936200. Its totient is φ = 675580439016.

The previous prime is 691665687551. The next prime is 691665687611. The reversal of 691665687607 is 706786566196.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 691665687607 - 2¹¹ = 691665685559 is a prime.

It is a super-2 number, since 2×691665687607² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (691665687697) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8042624232 + ... + 8042624317.

It is an arithmetic number, because the mean of its divisors is an integer number (176937734050).

Almost surely, 2^691665687607 is an apocalyptic number.

691665687607 is a deficient number, since it is larger than the sum of its proper divisors (16085248593).

691665687607 is a wasteful number, since it uses less digits than its factorization.

691665687607 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16085248592.

The product of its (nonzero) digits is 137168640, while the sum is 67.

The spelling of 691665687607 in words is "six hundred ninety-one billion, six hundred sixty-five million, six hundred eighty-seven thousand, six hundred seven".