661678 has 4 divisors (see below), whose sum is σ = 992520. Its totient is φ = 330838.

The previous prime is 661673. The next prime is 661679. The reversal of 661678 is 876166.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661673) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 165418 + ... + 165421.

It is an arithmetic number, because the mean of its divisors is an integer number (248130).

2⁶⁶¹⁶⁷⁸ is an apocalyptic number.

661678 is a deficient number, since it is larger than the sum of its proper divisors (330842).

661678 is a wasteful number, since it uses less digits than its factorization.

661678 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 330841.

The product of its digits is 12096, while the sum is 34.

The square root of 661678 is about 813.4359224917. The cubic root of 661678 is about 87.1396006001.

The spelling of 661678 in words is "six hundred sixty-one thousand, six hundred seventy-eight".