128649640 has 32 divisors (see below), whose sum is σ = 330814080. Its totient is φ = 44108352.

The previous prime is 128649611. The next prime is 128649641. The reversal of 128649640 is 46946821.

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a junction number, because it is equal to n+sod(n) for n = 128649593 and 128649602.

It is not an unprimeable number, because it can be changed into a prime (128649641) 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 7 ways as a sum of consecutive naturals, for example, 229452 + ... + 230011.

It is an arithmetic number, because the mean of its divisors is an integer number (10337940).

Almost surely, 2^128649640 is an apocalyptic number.

128649640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

128649640 is an abundant number, since it is smaller than the sum of its proper divisors (202164440).

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

128649640 is a wasteful number, since it uses less digits than its factorization.

128649640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 459481 (or 459477 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 40.

The square root of 128649640 is about 11342.3824657785. The cubic root of 128649640 is about 504.8195806828.

The spelling of 128649640 in words is "one hundred twenty-eight million, six hundred forty-nine thousand, six hundred forty".