661525128 has 96 divisors (see below), whose sum is σ = 2057421600. Its totient is φ = 189907200.

The previous prime is 661525127. The next prime is 661525129. The reversal of 661525128 is 821525166.

661525128 is a `hidden beast` number, since 6 + 6 + 1 + 525 + 128 = 666.

It is an interprime number because it is at equal distance from previous prime (661525127) and next prime (661525129).

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 = 661525092 and 661525101.

It is not an unprimeable number, because it can be changed into a prime (661525121) 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 23 ways as a sum of consecutive naturals, for example, 6933 + ... + 37028.

It is an arithmetic number, because the mean of its divisors is an integer number (21431475).

Almost surely, 2^661525128 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 661525128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1028710800).

661525128 is an abundant number, since it is smaller than the sum of its proper divisors (1395896472).

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

661525128 is a wasteful number, since it uses less digits than its factorization.

661525128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44003 (or 43996 counting only the distinct ones).

The product of its digits is 28800, while the sum is 36.

The square root of 661525128 is about 25720.1307928245. The cubic root of 661525128 is about 871.3288926362.

The spelling of 661525128 in words is "six hundred sixty-one million, five hundred twenty-five thousand, one hundred twenty-eight".