643131109 has 2 divisors, whose sum is σ = 643131110. Its totient is φ = 643131108.

The previous prime is 643131107. The next prime is 643131143. The reversal of 643131109 is 901131346.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 380367009 + 262764100 = 19503^2 + 16210^2 .

It is a cyclic number.

It is not a de Polignac number, because 643131109 - 2¹ = 643131107 is a prime.

Together with 643131107, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643131101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321565554 + 321565555.

It is an arithmetic number, because the mean of its divisors is an integer number (321565555).

Almost surely, 2^643131109 is an apocalyptic number.

It is an amenable number.

643131109 is a deficient number, since it is larger than the sum of its proper divisors (1).

643131109 is an equidigital number, since it uses as much as digits as its factorization.

643131109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1944, while the sum is 28.

The square root of 643131109 is about 25360.0297515598. The cubic root of 643131109 is about 863.1769590845.

The spelling of 643131109 in words is "six hundred forty-three million, one hundred thirty-one thousand, one hundred nine".