643687601 has 4 divisors (see below), whose sum is σ = 646063104. Its totient is φ = 641312100.

The previous prime is 643687579. The next prime is 643687613. The reversal of 643687601 is 106786346.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 643687601 - 2⁶ = 643687537 is a prime.

It is a super-2 number, since 2×643687601² = 828667455362270402, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (643687651) 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, 1187345 + ... + 1187886.

It is an arithmetic number, because the mean of its divisors is an integer number (161515776).

Almost surely, 2^643687601 is an apocalyptic number.

It is an amenable number.

643687601 is a deficient number, since it is larger than the sum of its proper divisors (2375503).

643687601 is a wasteful number, since it uses less digits than its factorization.

643687601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2375502.

The product of its (nonzero) digits is 145152, while the sum is 41.

The square root of 643687601 is about 25370.9992116984. Note that the first 3 decimals coincide. The cubic root of 643687601 is about 863.4258521356.

The spelling of 643687601 in words is "six hundred forty-three million, six hundred eighty-seven thousand, six hundred one".