659991 has 8 divisors (see below), whose sum is σ = 931824. Its totient is φ = 414080.

The previous prime is 659983. The next prime is 659999. The reversal of 659991 is 199956.

It is an interprime number because it is at equal distance from previous prime (659983) and next prime (659999).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 659991 - 2³ = 659983 is a prime.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 659991.

It is not an unprimeable number, because it can be changed into a prime (659999) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6420 + ... + 6521.

It is an arithmetic number, because the mean of its divisors is an integer number (116478).

2⁶⁵⁹⁹⁹¹ is an apocalyptic number.

659991 is a deficient number, since it is larger than the sum of its proper divisors (271833).

659991 is a wasteful number, since it uses less digits than its factorization.

659991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12961.

The product of its digits is 21870, while the sum is 39.

The square root of 659991 is about 812.3983013276. The cubic root of 659991 is about 87.0654811560.

The spelling of 659991 in words is "six hundred fifty-nine thousand, nine hundred ninety-one".