644646042 has 24 divisors (see below), whose sum is σ = 1434484116. Its totient is φ = 209074176.

The previous prime is 644646011. The next prime is 644646043. The reversal of 644646042 is 240646446.

It is a happy number.

644646042 is a `hidden beast` number, since 6 + 4 + 4 + 646 + 0 + 4 + 2 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 606193641 + 38452401 = 24621^2 + 6201^2 .

It is a junction number, because it is equal to n+sod(n) for n = 644645988 and 644646006.

It is not an unprimeable number, because it can be changed into a prime (644646043) 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 11 ways as a sum of consecutive naturals, for example, 483303 + ... + 484634.

Almost surely, 2^644646042 is an apocalyptic number.

644646042 is an abundant number, since it is smaller than the sum of its proper divisors (789838074).

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

644646042 is a wasteful number, since it uses less digits than its factorization.

644646042 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 967982 (or 967979 counting only the distinct ones).

The product of its (nonzero) digits is 110592, while the sum is 36.

The square root of 644646042 is about 25389.8807007831. The cubic root of 644646042 is about 863.8541822461.

The spelling of 644646042 in words is "six hundred forty-four million, six hundred forty-six thousand, forty-two".