643755919 has 2 divisors, whose sum is σ = 643755920. Its totient is φ = 643755918.

The previous prime is 643755913. The next prime is 643755941. The reversal of 643755919 is 919557346.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 643755919 - 2⁹ = 643755407 is a prime.

It is a super-2 number, since 2×643755919² = 828843366495069122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643755913) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321877959 + 321877960.

It is an arithmetic number, because the mean of its divisors is an integer number (321877960).

Almost surely, 2^643755919 is an apocalyptic number.

643755919 is a deficient number, since it is larger than the sum of its proper divisors (1).

643755919 is an equidigital number, since it uses as much as digits as its factorization.

643755919 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1020600, while the sum is 49.

The square root of 643755919 is about 25372.3455557424. The cubic root of 643755919 is about 863.4563977194.

The spelling of 643755919 in words is "six hundred forty-three million, seven hundred fifty-five thousand, nine hundred nineteen".