643469909 has 2 divisors, whose sum is σ = 643469910. Its totient is φ = 643469908.

The previous prime is 643469887. The next prime is 643469929. The reversal of 643469909 is 909964346.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 637815025 + 5654884 = 25255^2 + 2378^2 .

It is a cyclic number.

It is not a de Polignac number, because 643469909 - 2⁸ = 643469653 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643469929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321734954 + 321734955.

It is an arithmetic number, because the mean of its divisors is an integer number (321734955).

Almost surely, 2^643469909 is an apocalyptic number.

It is an amenable number.

643469909 is a deficient number, since it is larger than the sum of its proper divisors (1).

643469909 is an equidigital number, since it uses as much as digits as its factorization.

643469909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1259712, while the sum is 50.

The square root of 643469909 is about 25366.7086749543. The cubic root of 643469909 is about 863.3285056933.

The spelling of 643469909 in words is "six hundred forty-three million, four hundred sixty-nine thousand, nine hundred nine".