666666444421 has 16 divisors (see below), whose sum is σ = 685611537408. Its totient is φ = 647851523200.

The previous prime is 666666444403. The next prime is 666666444467. The reversal of 666666444421 is 124444666666.

It is a cyclic number.

It is not a de Polignac number, because 666666444421 - 2¹⁷ = 666666313349 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666666444221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25057836 + ... + 25084426.

It is an arithmetic number, because the mean of its divisors is an integer number (42850721088).

Almost surely, 2^666666444421 is an apocalyptic number.

It is an amenable number.

666666444421 is a deficient number, since it is larger than the sum of its proper divisors (18945092987).

666666444421 is a wasteful number, since it uses less digits than its factorization.

666666444421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29012.

The product of its digits is 23887872, while the sum is 55.

The spelling of 666666444421 in words is "six hundred sixty-six billion, six hundred sixty-six million, four hundred forty-four thousand, four hundred twenty-one".