667778 has 8 divisors (see below), whose sum is σ = 1006668. Its totient is φ = 332224.

The previous prime is 667769. The next prime is 667781. The reversal of 667778 is 877766.

It can be written as a sum of positive squares in 2 ways, for example, as 667489 + 289 = 817^2 + 17^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Curzon number.

It is a plaindrome in base 10.

It is an unprimeable number.

667778 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 251 + ... + 1182.

2⁶⁶⁷⁷⁷⁸ is an apocalyptic number.

667778 is a deficient number, since it is larger than the sum of its proper divisors (338890).

667778 is a wasteful number, since it uses less digits than its factorization.

667778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1668.

The product of its digits is 98784, while the sum is 41.

The square root of 667778 is about 817.1768474449. The cubic root of 667778 is about 87.4065614799.

The spelling of 667778 in words is "six hundred sixty-seven thousand, seven hundred seventy-eight".