66788989 has 4 divisors (see below), whose sum is σ = 67380156. Its totient is φ = 66197824.

The previous prime is 66788963. The next prime is 66788999. The reversal of 66788989 is 98988766.

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

It can be written as a sum of positive squares in 2 ways, for example, as 12545764 + 54243225 = 3542^2 + 7365^2 .

It is a cyclic number.

It is not a de Polignac number, because 66788989 - 2²⁵ = 33234557 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66788999) 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 3 ways as a sum of consecutive naturals, for example, 295414 + ... + 295639.

It is an arithmetic number, because the mean of its divisors is an integer number (16845039).

Almost surely, 2^66788989 is an apocalyptic number.

It is an amenable number.

66788989 is a deficient number, since it is larger than the sum of its proper divisors (591167).

66788989 is a wasteful number, since it uses less digits than its factorization.

66788989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 591166.

The product of its digits is 10450944, while the sum is 61.

The square root of 66788989 is about 8172.4530589047. The cubic root of 66788989 is about 405.7279778951.

The spelling of 66788989 in words is "sixty-six million, seven hundred eighty-eight thousand, nine hundred eighty-nine".