666440669 has 2 divisors, whose sum is σ = 666440670. Its totient is φ = 666440668.

The previous prime is 666440657. The next prime is 666440689. The reversal of 666440669 is 966044666.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 651525625 + 14915044 = 25525^2 + 3862^2 .

It is a cyclic number.

It is not a de Polignac number, because 666440669 - 2⁴ = 666440653 is a prime.

It is a super-2 number, since 2×666440669² = 888286330594335122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666440689) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333220334 + 333220335.

It is an arithmetic number, because the mean of its divisors is an integer number (333220335).

Almost surely, 2^666440669 is an apocalyptic number.

It is an amenable number.

666440669 is a deficient number, since it is larger than the sum of its proper divisors (1).

666440669 is an equidigital number, since it uses as much as digits as its factorization.

666440669 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1119744, while the sum is 47.

The square root of 666440669 is about 25815.5121777586. The cubic root of 666440669 is about 873.4817400063.

The spelling of 666440669 in words is "six hundred sixty-six million, four hundred forty thousand, six hundred sixty-nine".