646669 has 2 divisors, whose sum is σ = 646670. Its totient is φ = 646668.

The previous prime is 646643. The next prime is 646687. The reversal of 646669 is 966646.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 476100 + 170569 = 690^2 + 413^2 .

It is a cyclic number.

It is not a de Polignac number, because 646669 - 2⁵ = 646637 is a prime.

It is a super-2 number, since 2×646669² = 836361591122, which contains 22 as substring.

646669 is a lucky number.

It is a nialpdrome in base 7.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (646609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323334 + 323335.

It is an arithmetic number, because the mean of its divisors is an integer number (323335).

2⁶⁴⁶⁶⁶⁹ is an apocalyptic number.

It is an amenable number.

646669 is a deficient number, since it is larger than the sum of its proper divisors (1).

646669 is an equidigital number, since it uses as much as digits as its factorization.

646669 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 46656, while the sum is 37.

The square root of 646669 is about 804.1573229164. The cubic root of 646669 is about 86.4756856383.

The spelling of 646669 in words is "six hundred forty-six thousand, six hundred sixty-nine".