661966 has 4 divisors (see below), whose sum is σ = 992952. Its totient is φ = 330982.

The previous prime is 661961. The next prime is 661987. The reversal of 661966 is 669166.

It is a happy number.

661966 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a super-3 number, since 3×661966³ = 870218488223330088, which contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 165490 + ... + 165493.

It is an arithmetic number, because the mean of its divisors is an integer number (248238).

2⁶⁶¹⁹⁶⁶ is an apocalyptic number.

661966 is a deficient number, since it is larger than the sum of its proper divisors (330986).

661966 is a wasteful number, since it uses less digits than its factorization.

661966 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 330985.

The product of its digits is 11664, while the sum is 34.

The square root of 661966 is about 813.6129300841. The cubic root of 661966 is about 87.1522414741.

The spelling of 661966 in words is "six hundred sixty-one thousand, nine hundred sixty-six".