666781428 has 12 divisors (see below), whose sum is σ = 1555823360. Its totient is φ = 222260472.

The previous prime is 666781417. The next prime is 666781439. The reversal of 666781428 is 824187666.

It is an interprime number because it is at equal distance from previous prime (666781417) and next prime (666781439).

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27782548 + ... + 27782571.

Almost surely, 2^666781428 is an apocalyptic number.

It is an amenable number.

666781428 is an abundant number, since it is smaller than the sum of its proper divisors (889041932).

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

666781428 is a wasteful number, since it uses less digits than its factorization.

666781428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55565126 (or 55565124 counting only the distinct ones).

The product of its digits is 774144, while the sum is 48.

The square root of 666781428 is about 25822.1112227486. Note that the first 3 decimals coincide. The cubic root of 666781428 is about 873.6305884897.

The spelling of 666781428 in words is "six hundred sixty-six million, seven hundred eighty-one thousand, four hundred twenty-eight".