66978589 has 4 divisors (see below), whose sum is σ = 70918524. Its totient is φ = 63038656.

The previous prime is 66978581. The next prime is 66978673. The reversal of 66978589 is 98587966.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 98587966 = 2 ⋅49293983.

It can be written as a sum of positive squares in 2 ways, for example, as 55756089 + 11222500 = 7467^2 + 3350^2 .

It is a cyclic number.

It is not a de Polignac number, because 66978589 - 2³ = 66978581 is a prime.

It is a super-2 number, since 2×66978589² = 8972262768861842, 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 (66978581) 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, 1969942 + ... + 1969975.

It is an arithmetic number, because the mean of its divisors is an integer number (17729631).

Almost surely, 2^66978589 is an apocalyptic number.

It is an amenable number.

66978589 is a deficient number, since it is larger than the sum of its proper divisors (3939935).

66978589 is a wasteful number, since it uses less digits than its factorization.

66978589 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3939934.

The product of its digits is 6531840, while the sum is 58.

The square root of 66978589 is about 8184.0447823799. The cubic root of 66978589 is about 406.1115408548. Note that the first 3 decimals are identical.

The spelling of 66978589 in words is "sixty-six million, nine hundred seventy-eight thousand, five hundred eighty-nine".