666545421 has 4 divisors (see below), whose sum is σ = 888727232. Its totient is φ = 444363612.

The previous prime is 666545387. The next prime is 666545431. The reversal of 666545421 is 124545666.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 666545421 - 2¹¹ = 666543373 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 666545421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666545431) 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, 111090901 + ... + 111090906.

It is an arithmetic number, because the mean of its divisors is an integer number (222181808).

Almost surely, 2^666545421 is an apocalyptic number.

It is an amenable number.

666545421 is a deficient number, since it is larger than the sum of its proper divisors (222181811).

666545421 is a wasteful number, since it uses less digits than its factorization.

666545421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 222181810.

The product of its digits is 172800, while the sum is 39.

The square root of 666545421 is about 25817.5409557146. The cubic root of 666545421 is about 873.5275026025.

The spelling of 666545421 in words is "six hundred sixty-six million, five hundred forty-five thousand, four hundred twenty-one".