643828657 has 2 divisors, whose sum is σ = 643828658. Its totient is φ = 643828656.

The previous prime is 643828651. The next prime is 643828663. The reversal of 643828657 is 756828346.

It is a balanced prime because it is at equal distance from previous prime (643828651) and next prime (643828663).

It can be written as a sum of positive squares in only one way, i.e., 427621041 + 216207616 = 20679^2 + 14704^2 .

It is a cyclic number.

It is not a de Polignac number, because 643828657 - 2³ = 643828649 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 643828657.

It is not a weakly prime, because it can be changed into another prime (643828651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321914328 + 321914329.

It is an arithmetic number, because the mean of its divisors is an integer number (321914329).

Almost surely, 2^643828657 is an apocalyptic number.

It is an amenable number.

643828657 is a deficient number, since it is larger than the sum of its proper divisors (1).

643828657 is an equidigital number, since it uses as much as digits as its factorization.

643828657 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1935360, while the sum is 49.

The square root of 643828657 is about 25373.7789262853. The cubic root of 643828657 is about 863.4889171491.

The spelling of 643828657 in words is "six hundred forty-three million, eight hundred twenty-eight thousand, six hundred fifty-seven".