643566437 has 4 divisors (see below), whose sum is σ = 643808460. Its totient is φ = 643324416.

The previous prime is 643566431. The next prime is 643566449. The reversal of 643566437 is 734665346.

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

It can be written as a sum of positive squares in 2 ways, for example, as 177049636 + 466516801 = 13306^2 + 21599^2 .

It is a cyclic number.

It is not a de Polignac number, because 643566437 - 2⁴ = 643566421 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643566431) 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, 116978 + ... + 122355.

It is an arithmetic number, because the mean of its divisors is an integer number (160952115).

Almost surely, 2^643566437 is an apocalyptic number.

It is an amenable number.

643566437 is a deficient number, since it is larger than the sum of its proper divisors (242023).

643566437 is a wasteful number, since it uses less digits than its factorization.

643566437 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 242022.

The product of its digits is 1088640, while the sum is 44.

The square root of 643566437 is about 25368.6112548559. The cubic root of 643566437 is about 863.3716733204.

The spelling of 643566437 in words is "six hundred forty-three million, five hundred sixty-six thousand, four hundred thirty-seven".