643213778 has 8 divisors (see below), whose sum is σ = 964987020. Its totient is φ = 321551440.

The previous prime is 643213763. The next prime is 643213789. The reversal of 643213778 is 877312346.

643213778 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 593750689 + 49463089 = 24367^2 + 7033^2 .

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

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11273 + ... + 37596.

Almost surely, 2^643213778 is an apocalyptic number.

643213778 is a deficient number, since it is larger than the sum of its proper divisors (321773242).

643213778 is a wasteful number, since it uses less digits than its factorization.

643213778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55452.

The product of its digits is 169344, while the sum is 41.

The square root of 643213778 is about 25361.6596065794. The cubic root of 643213778 is about 863.2139421702.

The spelling of 643213778 in words is "six hundred forty-three million, two hundred thirteen thousand, seven hundred seventy-eight".