6688817661 has 4 divisors (see below), whose sum is σ = 8918423552. Its totient is φ = 4459211772.

The previous prime is 6688817659. The next prime is 6688817711. The reversal of 6688817661 is 1667188866.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 6688817661 - 2¹ = 6688817659 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6688817621) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1114802941 + ... + 1114802946.

It is an arithmetic number, because the mean of its divisors is an integer number (2229605888).

Almost surely, 2^6688817661 is an apocalyptic number.

It is an amenable number.

6688817661 is a deficient number, since it is larger than the sum of its proper divisors (2229605891).

6688817661 is a wasteful number, since it uses less digits than its factorization.

6688817661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2229605890.

The product of its digits is 4644864, while the sum is 57.

The square root of 6688817661 is about 81785.1921866055. The cubic root of 6688817661 is about 1884.1542417141.

The spelling of 6688817661 in words is "six billion, six hundred eighty-eight million, eight hundred seventeen thousand, six hundred sixty-one".