656390128 has 40 divisors (see below), whose sum is σ = 1351721520. Its totient is φ = 307706880.

The previous prime is 656390117. The next prime is 656390129. The reversal of 656390128 is 821093656.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (656390129) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 68683 + ... + 77653.

It is an arithmetic number, because the mean of its divisors is an integer number (33793038).

Almost surely, 2^656390128 is an apocalyptic number.

656390128 is a gapful number since it is divisible by the number (68) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 656390128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (675860760).

656390128 is an abundant number, since it is smaller than the sum of its proper divisors (695331392).

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

656390128 is a wasteful number, since it uses less digits than its factorization.

656390128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9265 (or 9259 counting only the distinct ones).

The product of its (nonzero) digits is 77760, while the sum is 40.

The square root of 656390128 is about 25620.1117874220. Note that the first 3 decimals coincide. The cubic root of 656390128 is about 869.0685093482.

The spelling of 656390128 in words is "six hundred fifty-six million, three hundred ninety thousand, one hundred twenty-eight".