66665915 has 4 divisors (see below), whose sum is σ = 79999104. Its totient is φ = 53332728.

The previous prime is 66665909. The next prime is 66665933. The reversal of 66665915 is 51956666.

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 66665915 - 2¹⁶ = 66600379 is a prime.

It is a Duffinian 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 3 ways as a sum of consecutive naturals, for example, 6666587 + ... + 6666596.

It is an arithmetic number, because the mean of its divisors is an integer number (19999776).

Almost surely, 2^66665915 is an apocalyptic number.

66665915 is a deficient number, since it is larger than the sum of its proper divisors (13333189).

66665915 is a wasteful number, since it uses less digits than its factorization.

66665915 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13333188.

The product of its digits is 291600, while the sum is 44.

The square root of 66665915 is about 8164.9197791528. The cubic root of 66665915 is about 405.4786091030.

The spelling of 66665915 in words is "sixty-six million, six hundred sixty-five thousand, nine hundred fifteen".