661311 has 16 divisors (see below), whose sum is σ = 1120000. Its totient is φ = 377784.

The previous prime is 661267. The next prime is 661321. The reversal of 661311 is 113166.

661311 is a `hidden beast` number, since 661 + 3 + 1 + 1 = 666.

It is not a de Polignac number, because 661311 - 2⁷ = 661183 is a prime.

661311 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661321) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1561 + ... + 1938.

It is an arithmetic number, because the mean of its divisors is an integer number (70000).

2⁶⁶¹³¹¹ is an apocalyptic number.

661311 is a deficient number, since it is larger than the sum of its proper divisors (458689).

661311 is a wasteful number, since it uses less digits than its factorization.

661311 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3515 (or 3509 counting only the distinct ones).

The product of its digits is 108, while the sum is 18.

The square root of 661311 is about 813.2103049027. The cubic root of 661311 is about 87.1234869477.

Adding to 661311 its reverse (113166), we get a palindrome (774477).

The spelling of 661311 in words is "six hundred sixty-one thousand, three hundred eleven".