661728772 has 6 divisors (see below), whose sum is σ = 1158025358. Its totient is φ = 330864384.

The previous prime is 661728761. The next prime is 661728773. The reversal of 661728772 is 277827166.

It can be written as a sum of positive squares in only one way, i.e., 540376516 + 121352256 = 23246^2 + 11016^2 .

It is not an unprimeable number, because it can be changed into a prime (661728773) 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 as a sum of consecutive naturals, namely, 82716093 + ... + 82716100.

Almost surely, 2^661728772 is an apocalyptic number.

It is an amenable number.

661728772 is a deficient number, since it is larger than the sum of its proper divisors (496296586).

661728772 is a wasteful number, since it uses less digits than its factorization.

661728772 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165432197 (or 165432195 counting only the distinct ones).

The product of its digits is 395136, while the sum is 46.

The square root of 661728772 is about 25724.0893327636. The cubic root of 661728772 is about 871.4182934711.

The spelling of 661728772 in words is "six hundred sixty-one million, seven hundred twenty-eight thousand, seven hundred seventy-two".