642556656 has 120 divisors (see below), whose sum is σ = 2061876960. Its totient is φ = 182988288.

The previous prime is 642556631. The next prime is 642556657. The reversal of 642556656 is 656655246.

It is a happy number.

642556656 is a `hidden beast` number, since 6 + 42 + 556 + 6 + 56 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (642556657) 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 23 ways as a sum of consecutive naturals, for example, 375130 + ... + 376838.

It is an arithmetic number, because the mean of its divisors is an integer number (17182308).

Almost surely, 2^642556656 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 642556656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1030938480).

642556656 is an abundant number, since it is smaller than the sum of its proper divisors (1419320304).

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

642556656 is a wasteful number, since it uses less digits than its factorization.

642556656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2103 (or 2094 counting only the distinct ones).

The product of its digits is 1296000, while the sum is 45.

The square root of 642556656 is about 25348.7012685068. The cubic root of 642556656 is about 862.9198822642.

The spelling of 642556656 in words is "six hundred forty-two million, five hundred fifty-six thousand, six hundred fifty-six".