643856471 has 4 divisors (see below), whose sum is σ = 652924944. Its totient is φ = 634788000.

The previous prime is 643856467. The next prime is 643856491. The reversal of 643856471 is 174658346.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 643856471 - 2² = 643856467 is a prime.

It is a super-3 number, since 3×643856471³ (a number of 27 digits) contains 333 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 (643856441) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4534130 + ... + 4534271.

It is an arithmetic number, because the mean of its divisors is an integer number (163231236).

Almost surely, 2^643856471 is an apocalyptic number.

643856471 is a deficient number, since it is larger than the sum of its proper divisors (9068473).

643856471 is an equidigital number, since it uses as much as digits as its factorization.

643856471 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9068472.

The product of its digits is 483840, while the sum is 44.

The square root of 643856471 is about 25374.3270058538. The cubic root of 643856471 is about 863.5013514796.

The spelling of 643856471 in words is "six hundred forty-three million, eight hundred fifty-six thousand, four hundred seventy-one".