66939779 has 4 divisors (see below), whose sum is σ = 67340784. Its totient is φ = 66538776.

The previous prime is 66939739. The next prime is 66939787. The reversal of 66939779 is 97793966.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 97793966 = 2 ⋅48896983.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66939779 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66939739) 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, 200252 + ... + 200585.

It is an arithmetic number, because the mean of its divisors is an integer number (16835196).

Almost surely, 2^66939779 is an apocalyptic number.

66939779 is a deficient number, since it is larger than the sum of its proper divisors (401005).

66939779 is a wasteful number, since it uses less digits than its factorization.

66939779 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 401004.

The product of its digits is 3857868, while the sum is 56.

The square root of 66939779 is about 8181.6733618496. The cubic root of 66939779 is about 406.0330867581.

The spelling of 66939779 in words is "sixty-six million, nine hundred thirty-nine thousand, seven hundred seventy-nine".