638669 has 2 divisors, whose sum is σ = 638670. Its totient is φ = 638668.

The previous prime is 638663. The next prime is 638689. The reversal of 638669 is 966836.

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., 570025 + 68644 = 755^2 + 262^2 .

It is a cyclic number.

It is not a de Polignac number, because 638669 - 2¹² = 634573 is a prime.

It is a super-2 number, since 2×638669² = 815796183122, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319334 + 319335.

It is an arithmetic number, because the mean of its divisors is an integer number (319335).

2⁶³⁸⁶⁶⁹ is an apocalyptic number.

It is an amenable number.

638669 is a deficient number, since it is larger than the sum of its proper divisors (1).

638669 is an equidigital number, since it uses as much as digits as its factorization.

638669 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 46656, while the sum is 38.

The square root of 638669 is about 799.1676920397. The cubic root of 638669 is about 86.1176054608.

The spelling of 638669 in words is "six hundred thirty-eight thousand, six hundred sixty-nine".