640249 has 2 divisors, whose sum is σ = 640250. Its totient is φ = 640248.

The previous prime is 640247. The next prime is 640259. The reversal of 640249 is 942046.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 480249 + 160000 = 693^2 + 400^2 .

It is a cyclic number.

It is not a de Polignac number, because 640249 - 2¹ = 640247 is a prime.

Together with 640247, it forms a pair of twin primes.

It is an Ulam number.

It is not a weakly prime, because it can be changed into another prime (640247) 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, 320124 + 320125.

It is an arithmetic number, because the mean of its divisors is an integer number (320125).

2⁶⁴⁰²⁴⁹ is an apocalyptic number.

It is an amenable number.

640249 is a deficient number, since it is larger than the sum of its proper divisors (1).

640249 is an equidigital number, since it uses as much as digits as its factorization.

640249 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1728, while the sum is 25.

The square root of 640249 is about 800.1556098660. The cubic root of 640249 is about 86.1885622821.

The spelling of 640249 in words is "six hundred forty thousand, two hundred forty-nine".