643968215 has 32 divisors (see below), whose sum is σ = 866612736. Its totient is φ = 455333760.

The previous prime is 643968203. The next prime is 643968217. The reversal of 643968215 is 512869346.

643968215 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a de Polignac number, because none of the positive numbers 2^k-643968215 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643968217) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 654614 + ... + 655596.

It is an arithmetic number, because the mean of its divisors is an integer number (27081648).

Almost surely, 2^643968215 is an apocalyptic number.

643968215 is a deficient number, since it is larger than the sum of its proper divisors (222644521).

643968215 is a wasteful number, since it uses less digits than its factorization.

643968215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1319.

The product of its digits is 311040, while the sum is 44.

The square root of 643968215 is about 25376.5288209400. The cubic root of 643968215 is about 863.5513033543.

It can be divided in two parts, 643968 and 215, that multiplied together give a triangular number (138453120 = T₁₆₆₄₀).

The spelling of 643968215 in words is "six hundred forty-three million, nine hundred sixty-eight thousand, two hundred fifteen".