643604581 has 4 divisors (see below), whose sum is σ = 681463692. Its totient is φ = 605745472.

The previous prime is 643604579. The next prime is 643604587. The reversal of 643604581 is 185406346.

It is a happy number.

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 521391556 + 122213025 = 22834^2 + 11055^2 .

It is a cyclic number.

It is not a de Polignac number, because 643604581 - 2¹ = 643604579 is a prime.

It is a super-2 number, since 2×643604581² = 828453713368371122, which contains 22 as substring.

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 643604581.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643604587) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18929530 + ... + 18929563.

It is an arithmetic number, because the mean of its divisors is an integer number (170365923).

Almost surely, 2^643604581 is an apocalyptic number.

It is an amenable number.

643604581 is a deficient number, since it is larger than the sum of its proper divisors (37859111).

643604581 is a wasteful number, since it uses less digits than its factorization.

643604581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37859110.

The product of its (nonzero) digits is 69120, while the sum is 37.

The square root of 643604581 is about 25369.3630389097. The cubic root of 643604581 is about 863.3887302481.

The spelling of 643604581 in words is "six hundred forty-three million, six hundred four thousand, five hundred eighty-one".