66945639 has 4 divisors (see below), whose sum is σ = 89260856. Its totient is φ = 44630424.

The previous prime is 66945587. The next prime is 66945649. The reversal of 66945639 is 93654966.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 66945639 - 2¹⁶ = 66880103 is a prime.

It is a super-2 number, since 2×66945639² = 8963437162236642, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66945649) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11157604 + ... + 11157609.

It is an arithmetic number, because the mean of its divisors is an integer number (22315214).

Almost surely, 2^66945639 is an apocalyptic number.

66945639 is a deficient number, since it is larger than the sum of its proper divisors (22315217).

66945639 is a wasteful number, since it uses less digits than its factorization.

66945639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22315216.

The product of its digits is 1049760, while the sum is 48.

The square root of 66945639 is about 8182.0314714623. The cubic root of 66945639 is about 406.0449346434.

The spelling of 66945639 in words is "sixty-six million, nine hundred forty-five thousand, six hundred thirty-nine".