720755666 has 4 divisors (see below), whose sum is σ = 1081133502. Its totient is φ = 360377832.

The previous prime is 720755663. The next prime is 720755677. The reversal of 720755666 is 666557027.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 666557027 = 661 ⋅1008407.

It can be written as a sum of positive squares in only one way, i.e., 708358225 + 12397441 = 26615^2 + 3521^2 .

It is a super-3 number, since 3×720755666³ (a number of 28 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not an unprimeable number, because it can be changed into a prime (720755663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 180188915 + ... + 180188918.

Almost surely, 2^720755666 is an apocalyptic number.

720755666 is a deficient number, since it is larger than the sum of its proper divisors (360377836).

720755666 is a wasteful number, since it uses less digits than its factorization.

720755666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 360377835.

The product of its (nonzero) digits is 529200, while the sum is 44.

The square root of 720755666 is about 26846.8930418401. The cubic root of 720755666 is about 896.5943994186.

The spelling of 720755666 in words is "seven hundred twenty million, seven hundred fifty-five thousand, six hundred sixty-six".