643923757 has 2 divisors, whose sum is σ = 643923758. Its totient is φ = 643923756.

The previous prime is 643923727. The next prime is 643923769. The reversal of 643923757 is 757329346.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 531118116 + 112805641 = 23046^2 + 10621^2 .

It is a cyclic number.

It is not a de Polignac number, because 643923757 - 2⁷ = 643923629 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643923727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321961878 + 321961879.

It is an arithmetic number, because the mean of its divisors is an integer number (321961879).

Almost surely, 2^643923757 is an apocalyptic number.

It is an amenable number.

643923757 is a deficient number, since it is larger than the sum of its proper divisors (1).

643923757 is an equidigital number, since it uses as much as digits as its factorization.

643923757 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 952560, while the sum is 46.

The square root of 643923757 is about 25375.6528388926. The cubic root of 643923757 is about 863.5314304028.

It can be divided in two parts, 643923 and 757, that added together give a triangular number (644680 = T₁₁₃₅).

The spelling of 643923757 in words is "six hundred forty-three million, nine hundred twenty-three thousand, seven hundred fifty-seven".