643721585 has 48 divisors (see below), whose sum is σ = 883145424. Its totient is φ = 447676416.

The previous prime is 643721579. The next prime is 643721599. The reversal of 643721585 is 585127346.

It can be written as a sum of positive squares in 8 ways, for example, as 110481121 + 533240464 = 10511^2 + 23092^2 .

It is not a de Polignac number, because 643721585 - 2⁴ = 643721569 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 3335249 + ... + 3335441.

It is an arithmetic number, because the mean of its divisors is an integer number (18398863).

Almost surely, 2^643721585 is an apocalyptic number.

643721585 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

643721585 is a deficient number, since it is larger than the sum of its proper divisors (239423839).

643721585 is a wasteful number, since it uses less digits than its factorization.

643721585 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 354 (or 331 counting only the distinct ones).

The product of its digits is 201600, while the sum is 41.

The square root of 643721585 is about 25371.6689439225. The cubic root of 643721585 is about 863.4410469536.

The spelling of 643721585 in words is "six hundred forty-three million, seven hundred twenty-one thousand, five hundred eighty-five".