645280128 has 256 divisors, whose sum is σ = 2075904000. Its totient is φ = 196577280.

The previous prime is 645280123. The next prime is 645280201. The reversal of 645280128 is 821082546.

645280128 is a `hidden beast` number, since 6 + 4 + 528 + 0 + 128 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 645280092 and 645280101.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645280121) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2035426 + ... + 2035742.

It is an arithmetic number, because the mean of its divisors is an integer number (8109000).

Almost surely, 2^645280128 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 645280128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1037952000).

645280128 is an abundant number, since it is smaller than the sum of its proper divisors (1430623872).

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

645280128 is a wasteful number, since it uses less digits than its factorization.

645280128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 390 (or 372 counting only the distinct ones).

The product of its (nonzero) digits is 30720, while the sum is 36.

The square root of 645280128 is about 25402.3646143425. The cubic root of 645280128 is about 864.1373238517.

The spelling of 645280128 in words is "six hundred forty-five million, two hundred eighty thousand, one hundred twenty-eight".