66644778 has 16 divisors (see below), whose sum is σ = 136126080. Its totient is φ = 21742176.

The previous prime is 66644759. The next prime is 66644791. The reversal of 66644778 is 87744666.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 117883 + ... + 118446.

It is an arithmetic number, because the mean of its divisors is an integer number (8507880).

Almost surely, 2^66644778 is an apocalyptic number.

66644778 is an abundant number, since it is smaller than the sum of its proper divisors (69481302).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

66644778 is a wasteful number, since it uses less digits than its factorization.

66644778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 236381.

The product of its digits is 1354752, while the sum is 48.

The square root of 66644778 is about 8163.6252976236. The cubic root of 66644778 is about 405.4357510832.

The spelling of 66644778 in words is "sixty-six million, six hundred forty-four thousand, seven hundred seventy-eight".