64640128 has 64 divisors (see below), whose sum is σ = 154958400. Its totient is φ = 26237952.

The previous prime is 64640123. The next prime is 64640129. The reversal of 64640128 is 82104646.

It is a tau number, because it is divible by the number of its divisors (64).

It is a super-2 number, since 2×64640128² = 8356692295712768, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 64640128.

It is not an unprimeable number, because it can be changed into a prime (64640123) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15126 + ... + 18922.

It is an arithmetic number, because the mean of its divisors is an integer number (2421225).

Almost surely, 2^64640128 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 64640128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (77479200).

64640128 is an abundant number, since it is smaller than the sum of its proper divisors (90318272).

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

64640128 is a wasteful number, since it uses less digits than its factorization.

64640128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3837 (or 3825 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 31.

The square root of 64640128 is about 8039.9084571903. The cubic root of 64640128 is about 401.3291783202.

The spelling of 64640128 in words is "sixty-four million, six hundred forty thousand, one hundred twenty-eight".