669778 has 4 divisors (see below), whose sum is σ = 1004670. Its totient is φ = 334888.

The previous prime is 669763. The next prime is 669787. The reversal of 669778 is 877966.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 877966 = 2 ⋅438983.

It can be written as a sum of positive squares in only one way, i.e., 603729 + 66049 = 777^2 + 257^2 .

It is an unprimeable number.

669778 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 as a sum of consecutive naturals, namely, 167443 + ... + 167446.

2⁶⁶⁹⁷⁷⁸ is an apocalyptic number.

669778 is a deficient number, since it is larger than the sum of its proper divisors (334892).

669778 is a wasteful number, since it uses less digits than its factorization.

669778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 334891.

The product of its digits is 127008, while the sum is 43.

The square root of 669778 is about 818.3996578689. The cubic root of 669778 is about 87.4937356059.

The spelling of 669778 in words is "six hundred sixty-nine thousand, seven hundred seventy-eight".