643729 has 2 divisors, whose sum is σ = 643730. Its totient is φ = 643728.

The previous prime is 643723. The next prime is 643751. The reversal of 643729 is 927346.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 603729 + 40000 = 777^2 + 200^2 .

It is a cyclic number.

It is not a de Polignac number, because 643729 - 2⁵ = 643697 is a prime.

It is a d-powerful number, because it can be written as 6⁶ + 4⁸ + 7 + 3¹² + 2³ + 9² .

It is a self number, because there is not a number n which added to its sum of digits gives 643729.

It is not a weakly prime, because it can be changed into another prime (643723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321864 + 321865.

It is an arithmetic number, because the mean of its divisors is an integer number (321865).

2⁶⁴³⁷²⁹ is an apocalyptic number.

It is an amenable number.

643729 is a deficient number, since it is larger than the sum of its proper divisors (1).

643729 is an equidigital number, since it uses as much as digits as its factorization.

643729 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9072, while the sum is 31.

The square root of 643729 is about 802.3272399713. The cubic root of 643729 is about 86.3444362254.

The spelling of 643729 in words is "six hundred forty-three thousand, seven hundred twenty-nine".