65666391 has 16 divisors (see below), whose sum is σ = 100176384. Its totient is φ = 37481184.

The previous prime is 65666387. The next prime is 65666407. The reversal of 65666391 is 19366656.

It is not a de Polignac number, because 65666391 - 2² = 65666387 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (65666371) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 34630 + ... + 36476.

It is an arithmetic number, because the mean of its divisors is an integer number (6261024).

Almost surely, 2^65666391 is an apocalyptic number.

65666391 is a deficient number, since it is larger than the sum of its proper divisors (34509993).

65666391 is a wasteful number, since it uses less digits than its factorization.

65666391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3550.

The product of its digits is 174960, while the sum is 42.

The square root of 65666391 is about 8103.4801782938. The cubic root of 65666391 is about 403.4419454933.

The spelling of 65666391 in words is "sixty-five million, six hundred sixty-six thousand, three hundred ninety-one".