666690 has 32 divisors (see below), whose sum is σ = 1627776. Its totient is φ = 174720.

The previous prime is 666683. The next prime is 666697. The reversal of 666690 is 96666.

666690 = T₁₀₀ + T₁₀₁ + ... + T₁₇₀.

It is an interprime number because it is at equal distance from previous prime (666683) and next prime (666697).

It is a super-2 number, since 2×666690² = 888951112200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (666697) by changing a digit.

666690 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1974 + ... + 2286.

It is an arithmetic number, because the mean of its divisors is an integer number (50868).

2⁶⁶⁶⁶⁹⁰ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 666690, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (813888).

666690 is an abundant number, since it is smaller than the sum of its proper divisors (961086).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

666690 is a wasteful number, since it uses less digits than its factorization.

666690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 394.

The product of its (nonzero) digits is 11664, while the sum is 33.

The square root of 666690 is about 816.5108694929. The cubic root of 666690 is about 87.3590656389.

The spelling of 666690 in words is "six hundred sixty-six thousand, six hundred ninety".