66400065 has 24 divisors (see below), whose sum is σ = 115283688. Its totient is φ = 35354880.

The previous prime is 66400063. The next prime is 66400069. The reversal of 66400065 is 56000466.

It can be written as a sum of positive squares in 4 ways, for example, as 5419584 + 60980481 = 2328^2 + 7809^2 .

It is not a de Polignac number, because 66400065 - 2¹ = 66400063 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66400063) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 49605 + ... + 50925.

It is an arithmetic number, because the mean of its divisors is an integer number (4803487).

Almost surely, 2^66400065 is an apocalyptic number.

It is an amenable number.

66400065 is a deficient number, since it is larger than the sum of its proper divisors (48883623).

66400065 is a wasteful number, since it uses less digits than its factorization.

66400065 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2449 (or 2446 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 27.

The square root of 66400065 is about 8148.6235033900. The cubic root of 66400065 is about 404.9389025347.

The spelling of 66400065 in words is "sixty-six million, four hundred thousand, sixty-five".