66991284 has 18 divisors (see below), whose sum is σ = 169339170. Its totient is φ = 22330416.

The previous prime is 66991273. The next prime is 66991307. The reversal of 66991284 is 48219966.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 62062884 + 4928400 = 7878^2 + 2220^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 930399 + ... + 930470.

Almost surely, 2^66991284 is an apocalyptic number.

It is an amenable number.

66991284 is an abundant number, since it is smaller than the sum of its proper divisors (102347886).

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

66991284 is a wasteful number, since it uses less digits than its factorization.

66991284 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1860879 (or 1860874 counting only the distinct ones).

The product of its digits is 186624, while the sum is 45.

The square root of 66991284 is about 8184.8203401174. The cubic root of 66991284 is about 406.1371971150.

The spelling of 66991284 in words is "sixty-six million, nine hundred ninety-one thousand, two hundred eighty-four".