1666412621 has 2 divisors, whose sum is σ = 1666412622. Its totient is φ = 1666412620.

The previous prime is 1666412603. The next prime is 1666412647. The reversal of 1666412621 is 1262146661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1010540521 + 655872100 = 31789^2 + 25610^2 .

It is an emirp because it is prime and its reverse (1262146661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1666412621 - 2⁶ = 1666412557 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1666412021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 833206310 + 833206311.

It is an arithmetic number, because the mean of its divisors is an integer number (833206311).

Almost surely, 2^1666412621 is an apocalyptic number.

It is an amenable number.

1666412621 is a deficient number, since it is larger than the sum of its proper divisors (1).

1666412621 is an equidigital number, since it uses as much as digits as its factorization.

1666412621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20736, while the sum is 35.

The square root of 1666412621 is about 40821.7175165377. The cubic root of 1666412621 is about 1185.5708575469.

The spelling of 1666412621 in words is "one billion, six hundred sixty-six million, four hundred twelve thousand, six hundred twenty-one".