66128989 has 4 divisors (see below), whose sum is σ = 66148156. Its totient is φ = 66109824.

The previous prime is 66128981. The next prime is 66129013. The reversal of 66128989 is 98982166.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 98982166 = 2 ⋅49491083.

It can be written as a sum of positive squares in 2 ways, for example, as 19316025 + 46812964 = 4395^2 + 6842^2 .

It is a cyclic number.

It is not a de Polignac number, because 66128989 - 2³ = 66128981 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 (66128981) 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, 2814 + ... + 11839.

It is an arithmetic number, because the mean of its divisors is an integer number (16537039).

Almost surely, 2^66128989 is an apocalyptic number.

It is an amenable number.

66128989 is a deficient number, since it is larger than the sum of its proper divisors (19167).

66128989 is a wasteful number, since it uses less digits than its factorization.

66128989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19166.

The product of its digits is 373248, while the sum is 49.

The square root of 66128989 is about 8131.9732537681. The cubic root of 66128989 is about 404.3871011972.

The spelling of 66128989 in words is "sixty-six million, one hundred twenty-eight thousand, nine hundred eighty-nine".