66888889 has 2 divisors, whose sum is σ = 66888890. Its totient is φ = 66888888.

The previous prime is 66888883. The next prime is 66888907. The reversal of 66888889 is 98888866.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 57229225 + 9659664 = 7565^2 + 3108^2 .

It is a cyclic number.

It is not a de Polignac number, because 66888889 - 2⁹ = 66888377 is a prime.

It is a plaindrome in base 10.

It is not a weakly prime, because it can be changed into another prime (66888883) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33444444 + 33444445.

It is an arithmetic number, because the mean of its divisors is an integer number (33444445).

Almost surely, 2^66888889 is an apocalyptic number.

It is an amenable number.

66888889 is a deficient number, since it is larger than the sum of its proper divisors (1).

66888889 is an equidigital number, since it uses as much as digits as its factorization.

66888889 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10616832, while the sum is 61.

The square root of 66888889 is about 8178.5627710497. The cubic root of 66888889 is about 405.9301670764.

The spelling of 66888889 in words is "sixty-six million, eight hundred eighty-eight thousand, eight hundred eighty-nine".