647778 has 16 divisors (see below), whose sum is σ = 1308960. Its totient is φ = 213696.

The previous prime is 647771. The next prime is 647783. The reversal of 647778 is 877746.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (647771) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 138 + ... + 1146.

It is an arithmetic number, because the mean of its divisors is an integer number (81810).

2⁶⁴⁷⁷⁷⁸ is an apocalyptic number.

647778 is an abundant number, since it is smaller than the sum of its proper divisors (661182).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

647778 is a wasteful number, since it uses less digits than its factorization.

647778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1121.

The product of its digits is 65856, while the sum is 39.

The square root of 647778 is about 804.8465692292. The cubic root of 647778 is about 86.5250910093.

It can be divided in two parts, 6477 and 78, that added together give a triangular number (6555 = T₁₁₄).

The spelling of 647778 in words is "six hundred forty-seven thousand, seven hundred seventy-eight".