66865639 has 2 divisors, whose sum is σ = 66865640. Its totient is φ = 66865638.

The previous prime is 66865637. The next prime is 66865649. The reversal of 66865639 is 93656866.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 66865639 - 2¹ = 66865637 is a prime.

Together with 66865637, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 66865592 and 66865601.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66865633) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33432819 + 33432820.

It is an arithmetic number, because the mean of its divisors is an integer number (33432820).

Almost surely, 2^66865639 is an apocalyptic number.

66865639 is a deficient number, since it is larger than the sum of its proper divisors (1).

66865639 is an equidigital number, since it uses as much as digits as its factorization.

66865639 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1399680, while the sum is 49.

The square root of 66865639 is about 8177.1412486272. The cubic root of 66865639 is about 405.8831290194.

The spelling of 66865639 in words is "sixty-six million, eight hundred sixty-five thousand, six hundred thirty-nine".