646054778 has 4 divisors (see below), whose sum is σ = 969082170. Its totient is φ = 323027388.

The previous prime is 646054771. The next prime is 646054847. The reversal of 646054778 is 877450646.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 877450646 = 2 ⋅438725323.

It can be written as a sum of positive squares in only one way, i.e., 644499769 + 1555009 = 25387^2 + 1247^2 .

It is not an unprimeable number, because it can be changed into a prime (646054771) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161513693 + ... + 161513696.

Almost surely, 2^646054778 is an apocalyptic number.

646054778 is a deficient number, since it is larger than the sum of its proper divisors (323027392).

646054778 is a wasteful number, since it uses less digits than its factorization.

646054778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 323027391.

The product of its (nonzero) digits is 1128960, while the sum is 47.

The square root of 646054778 is about 25417.6076372266. The cubic root of 646054778 is about 864.4829805968.

The spelling of 646054778 in words is "six hundred forty-six million, fifty-four thousand, seven hundred seventy-eight".