666254021 has 4 divisors (see below), whose sum is σ = 705445452. Its totient is φ = 627062592.

The previous prime is 666254009. The next prime is 666254051. The reversal of 666254021 is 120452666.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 423330625 + 242923396 = 20575^2 + 15586^2 .

It is a cyclic number.

It is not a de Polignac number, because 666254021 - 2⁶ = 666253957 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 (666254051) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19595690 + ... + 19595723.

It is an arithmetic number, because the mean of its divisors is an integer number (176361363).

Almost surely, 2^666254021 is an apocalyptic number.

It is an amenable number.

666254021 is a deficient number, since it is larger than the sum of its proper divisors (39191431).

666254021 is a wasteful number, since it uses less digits than its factorization.

666254021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39191430.

The product of its (nonzero) digits is 17280, while the sum is 32.

The square root of 666254021 is about 25811.8968888379. The cubic root of 666254021 is about 873.4001879393.

The spelling of 666254021 in words is "six hundred sixty-six million, two hundred fifty-four thousand, twenty-one".