643751 has 2 divisors, whose sum is σ = 643752. Its totient is φ = 643750.

The previous prime is 643729. The next prime is 643781. The reversal of 643751 is 157346.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 643751 - 2¹⁸ = 381607 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 643751.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 643751.

It is not a weakly prime, because it can be changed into another prime (643781) 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, 321875 + 321876.

It is an arithmetic number, because the mean of its divisors is an integer number (321876).

2⁶⁴³⁷⁵¹ is an apocalyptic number.

643751 is a deficient number, since it is larger than the sum of its proper divisors (1).

643751 is an equidigital number, since it uses as much as digits as its factorization.

643751 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2520, while the sum is 26.

The square root of 643751 is about 802.3409499708. The cubic root of 643751 is about 86.3454198463.

The spelling of 643751 in words is "six hundred forty-three thousand, seven hundred fifty-one".