661611 has 4 divisors (see below), whose sum is σ = 882152. Its totient is φ = 441072.

The previous prime is 661607. The next prime is 661613. The reversal of 661611 is 116166.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 661611 - 2² = 661607 is a prime.

It is a D-number.

It is a Duffinian number.

661611 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (661613) 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, 110266 + ... + 110271.

It is an arithmetic number, because the mean of its divisors is an integer number (220538).

2⁶⁶¹⁶¹¹ is an apocalyptic number.

661611 is a deficient number, since it is larger than the sum of its proper divisors (220541).

661611 is a wasteful number, since it uses less digits than its factorization.

661611 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 220540.

The product of its digits is 216, while the sum is 21.

The square root of 661611 is about 813.3947381192. The cubic root of 661611 is about 87.1366593153.

Adding to 661611 its reverse (116166), we get a palindrome (777777).

The spelling of 661611 in words is "six hundred sixty-one thousand, six hundred eleven".