661171728 has 80 divisors (see below), whose sum is σ = 2054789120. Its totient is φ = 178962048.

The previous prime is 661171723. The next prime is 661171739. The reversal of 661171728 is 827171166.

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (661171723) 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 15 ways as a sum of consecutive naturals, for example, 45400 + ... + 58167.

It is an arithmetic number, because the mean of its divisors is an integer number (25684864).

Almost surely, 2^661171728 is an apocalyptic number.

It is an amenable number.

661171728 is an abundant number, since it is smaller than the sum of its proper divisors (1393617392).

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

661171728 is a wasteful number, since it uses less digits than its factorization.

661171728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 103604 (or 103598 counting only the distinct ones).

The product of its digits is 28224, while the sum is 39.

The square root of 661171728 is about 25713.2597700097. The cubic root of 661171728 is about 871.1737045375.

The spelling of 661171728 in words is "six hundred sixty-one million, one hundred seventy-one thousand, seven hundred twenty-eight".