643640901 has 8 divisors (see below), whose sum is σ = 895500480. Its totient is φ = 410437632.

The previous prime is 643640857. The next prime is 643640909. The reversal of 643640901 is 109046346.

643640901 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 643640901 - 2¹³ = 643632709 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643640909) 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, 4663996 + ... + 4664133.

It is an arithmetic number, because the mean of its divisors is an integer number (111937560).

Almost surely, 2^643640901 is an apocalyptic number.

It is an amenable number.

643640901 is a deficient number, since it is larger than the sum of its proper divisors (251859579).

643640901 is a wasteful number, since it uses less digits than its factorization.

643640901 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9328155.

The product of its (nonzero) digits is 15552, while the sum is 33.

The square root of 643640901 is about 25370.0788528534. The cubic root of 643640901 is about 863.4049709077.

The spelling of 643640901 in words is "six hundred forty-three million, six hundred forty thousand, nine hundred one".