643991019 has 8 divisors (see below), whose sum is σ = 981319680. Its totient is φ = 367994856.

The previous prime is 643991009. The next prime is 643991021. The reversal of 643991019 is 910199346.

643991019 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 643991019 - 2⁴ = 643991003 is a prime.

It is a super-2 number, since 2×643991019² = 829448865105316722, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (643991009) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15333099 + ... + 15333140.

It is an arithmetic number, because the mean of its divisors is an integer number (122664960).

Almost surely, 2^643991019 is an apocalyptic number.

643991019 is a deficient number, since it is larger than the sum of its proper divisors (337328661).

643991019 is a wasteful number, since it uses less digits than its factorization.

643991019 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30666249.

The product of its (nonzero) digits is 52488, while the sum is 42.

The square root of 643991019 is about 25376.9781297932. The cubic root of 643991019 is about 863.5614965031.

The spelling of 643991019 in words is "six hundred forty-three million, nine hundred ninety-one thousand, nineteen".