666563641 has 2 divisors, whose sum is σ = 666563642. Its totient is φ = 666563640.

The previous prime is 666563629. The next prime is 666563687. The reversal of 666563641 is 146365666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 428324416 + 238239225 = 20696^2 + 15435^2 .

It is a cyclic number.

It is not a de Polignac number, because 666563641 - 2¹⁵ = 666530873 is a prime.

It is not a weakly prime, because it can be changed into another prime (666563141) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333281820 + 333281821.

It is an arithmetic number, because the mean of its divisors is an integer number (333281821).

Almost surely, 2^666563641 is an apocalyptic number.

It is an amenable number.

666563641 is a deficient number, since it is larger than the sum of its proper divisors (1).

666563641 is an equidigital number, since it uses as much as digits as its factorization.

666563641 is an evil number, because the sum of its binary digits is even.

The product of its digits is 466560, while the sum is 43.

The square root of 666563641 is about 25817.8938141747. The cubic root of 666563641 is about 873.5354618131.

The spelling of 666563641 in words is "six hundred sixty-six million, five hundred sixty-three thousand, six hundred forty-one".