660721978 has 24 divisors (see below), whose sum is σ = 1168698132. Its totient is φ = 279284544.

The previous prime is 660721969. The next prime is 660721981. The reversal of 660721978 is 879127066.

It is a happy number.

660721978 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 652444849 + 8277129 = 25543^2 + 2877^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 39025 + ... + 53332.

Almost surely, 2^660721978 is an apocalyptic number.

660721978 is a deficient number, since it is larger than the sum of its proper divisors (507976154).

660721978 is a wasteful number, since it uses less digits than its factorization.

660721978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 92446 (or 92439 counting only the distinct ones).

The product of its (nonzero) digits is 254016, while the sum is 46.

The square root of 660721978 is about 25704.5127944491. The cubic root of 660721978 is about 870.9761263939.

The spelling of 660721978 in words is "six hundred sixty million, seven hundred twenty-one thousand, nine hundred seventy-eight".