661373728 has 12 divisors (see below), whose sum is σ = 1302079590. Its totient is φ = 330686848.

The previous prime is 661373723. The next prime is 661373743. The reversal of 661373728 is 827373166.

It can be written as a sum of positive squares in only one way, i.e., 441504144 + 219869584 = 21012^2 + 14828^2 .

It is a hoax number, since the sum of its digits (43) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (661373723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10333933 + ... + 10333996.

Almost surely, 2^661373728 is an apocalyptic number.

It is an amenable number.

661373728 is a deficient number, since it is larger than the sum of its proper divisors (640705862).

661373728 is a wasteful number, since it uses less digits than its factorization.

661373728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20667939 (or 20667931 counting only the distinct ones).

The product of its digits is 254016, while the sum is 43.

The square root of 661373728 is about 25717.1874045355. The cubic root of 661373728 is about 871.2624153128.

The spelling of 661373728 in words is "six hundred sixty-one million, three hundred seventy-three thousand, seven hundred twenty-eight".