643678121 has 2 divisors, whose sum is σ = 643678122. Its totient is φ = 643678120.

The previous prime is 643678109. The next prime is 643678153. The reversal of 643678121 is 121876346.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 503374096 + 140304025 = 22436^2 + 11845^2 .

It is a cyclic number.

It is not a de Polignac number, because 643678121 - 2¹⁴ = 643661737 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (643674121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321839060 + 321839061.

It is an arithmetic number, because the mean of its divisors is an integer number (321839061).

Almost surely, 2^643678121 is an apocalyptic number.

It is an amenable number.

643678121 is a deficient number, since it is larger than the sum of its proper divisors (1).

643678121 is an equidigital number, since it uses as much as digits as its factorization.

643678121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 48384, while the sum is 38.

The square root of 643678121 is about 25370.8123835245. The cubic root of 643678121 is about 863.4216133727.

The spelling of 643678121 in words is "six hundred forty-three million, six hundred seventy-eight thousand, one hundred twenty-one".