646778 has 8 divisors (see below), whose sum is σ = 1058400. Its totient is φ = 293980.

The previous prime is 646771. The next prime is 646781. The reversal of 646778 is 877646.

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

It is a nialpdrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (646771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14678 + ... + 14721.

It is an arithmetic number, because the mean of its divisors is an integer number (132300).

2⁶⁴⁶⁷⁷⁸ is an apocalyptic number.

646778 is a deficient number, since it is larger than the sum of its proper divisors (411622).

646778 is a wasteful number, since it uses less digits than its factorization.

646778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29412.

The product of its digits is 56448, while the sum is 38.

The square root of 646778 is about 804.2250928689. The cubic root of 646778 is about 86.4805440332.

The spelling of 646778 in words is "six hundred forty-six thousand, seven hundred seventy-eight".