665720001 has 12 divisors (see below), whose sum is σ = 962389012. Its totient is φ = 443447136.

The previous prime is 665719979. The next prime is 665720047. The reversal of 665720001 is 100027566.

665720001 is a `hidden beast` number, since 6 + 657 + 2 + 0 + 0 + 0 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 481846401 + 183873600 = 21951^2 + 13560^2 .

It is not a de Polignac number, because 665720001 - 2⁹ = 665719489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (665724001) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 18766 + ... + 41031.

Almost surely, 2^665720001 is an apocalyptic number.

It is an amenable number.

665720001 is a deficient number, since it is larger than the sum of its proper divisors (296669011).

665720001 is a wasteful number, since it uses less digits than its factorization.

665720001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61040 (or 61037 counting only the distinct ones).

The product of its (nonzero) digits is 2520, while the sum is 27.

The square root of 665720001 is about 25801.5503603950. The cubic root of 665720001 is about 873.1667745448.

Adding to 665720001 its reverse (100027566), we get a palindrome (765747567).

The spelling of 665720001 in words is "six hundred sixty-five million, seven hundred twenty thousand, one".