66905639 has 4 divisors (see below), whose sum is σ = 69212760. Its totient is φ = 64598520.

The previous prime is 66905633. The next prime is 66905677. The reversal of 66905639 is 93650966.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 93650966 = 2 ⋅46825483.

It is a cyclic number.

It is not a de Polignac number, because 66905639 - 2¹² = 66901543 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 66905639.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66905633) 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 in 3 ways as a sum of consecutive naturals, for example, 1153517 + ... + 1153574.

It is an arithmetic number, because the mean of its divisors is an integer number (17303190).

Almost surely, 2^66905639 is an apocalyptic number.

66905639 is a deficient number, since it is larger than the sum of its proper divisors (2307121).

66905639 is a wasteful number, since it uses less digits than its factorization.

66905639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2307120.

The product of its (nonzero) digits is 262440, while the sum is 44.

The square root of 66905639 is about 8179.5867255015. The cubic root of 66905639 is about 405.9640479542.

The spelling of 66905639 in words is "sixty-six million, nine hundred five thousand, six hundred thirty-nine".