656665691 has 4 divisors (see below), whose sum is σ = 716362584. Its totient is φ = 596968800.

The previous prime is 656665673. The next prime is 656665697. The reversal of 656665691 is 196566656.

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 656665691 - 2⁶ = 656665627 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (656665697) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 29848430 + ... + 29848451.

It is an arithmetic number, because the mean of its divisors is an integer number (179090646).

Almost surely, 2^656665691 is an apocalyptic number.

656665691 is a deficient number, since it is larger than the sum of its proper divisors (59696893).

656665691 is a wasteful number, since it uses less digits than its factorization.

656665691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59696892.

The product of its digits is 1749600, while the sum is 50.

The square root of 656665691 is about 25625.4890880155. The cubic root of 656665691 is about 869.1901085874.

The spelling of 656665691 in words is "six hundred fifty-six million, six hundred sixty-five thousand, six hundred ninety-one".