66640815 has 12 divisors (see below), whose sum is σ = 115510824. Its totient is φ = 35541744.

The previous prime is 66640807. The next prime is 66640829. The reversal of 66640815 is 51804666.

It is not a de Polignac number, because 66640815 - 2³ = 66640807 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 66640815.

It is a congruent number.

It is an unprimeable number.

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 in 11 ways as a sum of consecutive naturals, for example, 740409 + ... + 740498.

It is an arithmetic number, because the mean of its divisors is an integer number (9625902).

Almost surely, 2^66640815 is an apocalyptic number.

66640815 is a deficient number, since it is larger than the sum of its proper divisors (48870009).

66640815 is a wasteful number, since it uses less digits than its factorization.

66640815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1480918 (or 1480915 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 36.

The square root of 66640815 is about 8163.3825709690. The cubic root of 66640815 is about 405.4277145759.

The spelling of 66640815 in words is "sixty-six million, six hundred forty thousand, eight hundred fifteen".