666533621 has 8 divisors (see below), whose sum is σ = 728519904. Its totient is φ = 606078000.

The previous prime is 666533611. The next prime is 666533627. The reversal of 666533621 is 126335666.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 666533621 - 2¹⁸ = 666271477 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 (666533627) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 381755 + ... + 383496.

It is an arithmetic number, because the mean of its divisors is an integer number (91064988).

Almost surely, 2^666533621 is an apocalyptic number.

It is an amenable number.

666533621 is a deficient number, since it is larger than the sum of its proper divisors (61986283).

666533621 is a wasteful number, since it uses less digits than its factorization.

666533621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 765331.

The product of its digits is 116640, while the sum is 38.

The square root of 666533621 is about 25817.3124279039. The cubic root of 666533621 is about 873.5223478224.

The spelling of 666533621 in words is "six hundred sixty-six million, five hundred thirty-three thousand, six hundred twenty-one".