66128815 has 4 divisors (see below), whose sum is σ = 79354584. Its totient is φ = 52903048.

The previous prime is 66128807. The next prime is 66128837. The reversal of 66128815 is 51882166.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 66128815 - 2³ = 66128807 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, 6612877 + ... + 6612886.

It is an arithmetic number, because the mean of its divisors is an integer number (19838646).

Almost surely, 2^66128815 is an apocalyptic number.

66128815 is a deficient number, since it is larger than the sum of its proper divisors (13225769).

66128815 is a wasteful number, since it uses less digits than its factorization.

66128815 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13225768.

The product of its digits is 23040, while the sum is 37.

The square root of 66128815 is about 8131.9625552507. The cubic root of 66128815 is about 404.3867465196.

It can be divided in two parts, 66 and 128815, that added together give a square (128881 = 359²).

The spelling of 66128815 in words is "sixty-six million, one hundred twenty-eight thousand, eight hundred fifteen".