643217391 has 6 divisors (see below), whose sum is σ = 929091800. Its totient is φ = 428811588.

The previous prime is 643217383. The next prime is 643217417. The reversal of 643217391 is 193712346.

643217391 is a `hidden beast` number, since 643 + 2 + 1 + 7 + 3 + 9 + 1 = 666.

It is not a de Polignac number, because 643217391 - 2³ = 643217383 is a prime.

It is a super-2 number, since 2×643217391² = 827457224169693762, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643217291) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 35734291 + ... + 35734308.

Almost surely, 2^643217391 is an apocalyptic number.

643217391 is a deficient number, since it is larger than the sum of its proper divisors (285874409).

643217391 is a wasteful number, since it uses less digits than its factorization.

643217391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71468605 (or 71468602 counting only the distinct ones).

The product of its digits is 27216, while the sum is 36.

The square root of 643217391 is about 25361.7308360451. The cubic root of 643217391 is about 863.2155584219.

The spelling of 643217391 in words is "six hundred forty-three million, two hundred seventeen thousand, three hundred ninety-one".