661659 has 4 divisors (see below), whose sum is σ = 882216. Its totient is φ = 441104.

The previous prime is 661621. The next prime is 661663. The reversal of 661659 is 956166.

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 661659 - 2¹¹ = 659611 is a prime.

It is a D-number.

661659 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (661679) 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, 110274 + ... + 110279.

It is an arithmetic number, because the mean of its divisors is an integer number (220554).

2⁶⁶¹⁶⁵⁹ is an apocalyptic number.

661659 is a deficient number, since it is larger than the sum of its proper divisors (220557).

661659 is a wasteful number, since it uses less digits than its factorization.

661659 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 220556.

The product of its digits is 9720, while the sum is 33.

The square root of 661659 is about 813.4242435531. The cubic root of 661659 is about 87.1387665246.

The spelling of 661659 in words is "six hundred sixty-one thousand, six hundred fifty-nine".