66388765 has 4 divisors (see below), whose sum is σ = 79666524. Its totient is φ = 53111008.

The previous prime is 66388733. The next prime is 66388771. The reversal of 66388765 is 56788366.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 56788366 = 2 ⋅28394183.

It can be written as a sum of positive squares in 2 ways, for example, as 38118276 + 28270489 = 6174^2 + 5317^2 .

It is a cyclic number.

It is not a de Polignac number, because 66388765 - 2⁵ = 66388733 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6638872 + ... + 6638881.

It is an arithmetic number, because the mean of its divisors is an integer number (19916631).

Almost surely, 2^66388765 is an apocalyptic number.

It is an amenable number.

66388765 is a deficient number, since it is larger than the sum of its proper divisors (13277759).

66388765 is a wasteful number, since it uses less digits than its factorization.

66388765 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13277758.

The product of its digits is 1451520, while the sum is 49.

The square root of 66388765 is about 8147.9301052476. The cubic root of 66388765 is about 404.9159303223.

The spelling of 66388765 in words is "sixty-six million, three hundred eighty-eight thousand, seven hundred sixty-five".