643632257 has 8 divisors (see below), whose sum is σ = 683166600. Its totient is φ = 604283904.

The previous prime is 643632251. The next prime is 643632259. The reversal of 643632257 is 752236346.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 156150016 + 487482241 = 12496^2 + 22079^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 643632257 - 2²⁰ = 642583681 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 643632257.

It is not an unprimeable number, because it can be changed into a prime (643632251) 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, 39332 + ... + 53237.

It is an arithmetic number, because the mean of its divisors is an integer number (85395825).

Almost surely, 2^643632257 is an apocalyptic number.

It is an amenable number.

643632257 is a deficient number, since it is larger than the sum of its proper divisors (39534343).

643632257 is a wasteful number, since it uses less digits than its factorization.

643632257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 92995.

The product of its digits is 181440, while the sum is 38.

The square root of 643632257 is about 25369.9084941196. The cubic root of 643632257 is about 863.4011057576.

The spelling of 643632257 in words is "six hundred forty-three million, six hundred thirty-two thousand, two hundred fifty-seven".