643777009 has 2 divisors, whose sum is σ = 643777010. Its totient is φ = 643777008.

The previous prime is 643777007. The next prime is 643777049. The reversal of 643777009 is 900777346.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 593409600 + 50367409 = 24360^2 + 7097^2 .

It is a cyclic number.

It is not a de Polignac number, because 643777009 - 2¹ = 643777007 is a prime.

Together with 643777007, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (643777007) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321888504 + 321888505.

It is an arithmetic number, because the mean of its divisors is an integer number (321888505).

Almost surely, 2^643777009 is an apocalyptic number.

It is an amenable number.

643777009 is a deficient number, since it is larger than the sum of its proper divisors (1).

643777009 is an equidigital number, since it uses as much as digits as its factorization.

643777009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 222264, while the sum is 43.

The square root of 643777009 is about 25372.7611623174. The cubic root of 643777009 is about 863.4658268089.

The spelling of 643777009 in words is "six hundred forty-three million, seven hundred seventy-seven thousand, nine".