660691 has 4 divisors (see below), whose sum is σ = 671584. Its totient is φ = 649800.

The previous prime is 660683. The next prime is 660719. The reversal of 660691 is 196066.

It is a happy number.

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 660691 - 2³ = 660683 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (660601) 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, 5355 + ... + 5476.

It is an arithmetic number, because the mean of its divisors is an integer number (167896).

2⁶⁶⁰⁶⁹¹ is an apocalyptic number.

660691 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

660691 is a deficient number, since it is larger than the sum of its proper divisors (10893).

660691 is a wasteful number, since it uses less digits than its factorization.

660691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10892.

The product of its (nonzero) digits is 1944, while the sum is 28.

The square root of 660691 is about 812.8290103091. The cubic root of 660691 is about 87.0962514254.

The spelling of 660691 in words is "six hundred sixty thousand, six hundred ninety-one".