660400128 has 144 divisors (see below), whose sum is σ = 1979490240. Its totient is φ = 219967488.

The previous prime is 660400123. The next prime is 660400129. The reversal of 660400128 is 821004066.

It is a tau number, because it is divible by the number of its divisors (144).

It is a super-2 number, since 2×660400128² = 872256658124832768, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (660400123) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 497001 + ... + 498327.

It is an arithmetic number, because the mean of its divisors is an integer number (13746460).

Almost surely, 2^660400128 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 660400128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (989745120).

660400128 is an abundant number, since it is smaller than the sum of its proper divisors (1319090112).

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

660400128 is an equidigital number, since it uses as much as digits as its factorization.

660400128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1364 (or 1332 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 27.

The square root of 660400128 is about 25698.2514580273. The cubic root of 660400128 is about 870.8346805186.

The spelling of 660400128 in words is "six hundred sixty million, four hundred thousand, one hundred twenty-eight".