646389778 has 24 divisors (see below), whose sum is σ = 1017902592. Its totient is φ = 307707984.

The previous prime is 646389739. The next prime is 646389791. The reversal of 646389778 is 877983646.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 126175 + ... + 131197.

It is an arithmetic number, because the mean of its divisors is an integer number (42412608).

Almost surely, 2^646389778 is an apocalyptic number.

646389778 is a deficient number, since it is larger than the sum of its proper divisors (371512814).

646389778 is a wasteful number, since it uses less digits than its factorization.

646389778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5146 (or 5109 counting only the distinct ones).

The product of its digits is 12192768, while the sum is 58.

The square root of 646389778 is about 25424.1967031409. The cubic root of 646389778 is about 864.6323754401.

The spelling of 646389778 in words is "six hundred forty-six million, three hundred eighty-nine thousand, seven hundred seventy-eight".