643571261 has 4 divisors (see below), whose sum is σ = 681428412. Its totient is φ = 605714112.

The previous prime is 643571231. The next prime is 643571263. The reversal of 643571261 is 162175346.

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 342028036 + 301543225 = 18494^2 + 17365^2 .

It is a cyclic number.

It is not a de Polignac number, because 643571261 - 2⁶ = 643571197 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 (643571263) 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, 18928550 + ... + 18928583.

It is an arithmetic number, because the mean of its divisors is an integer number (170357103).

Almost surely, 2^643571261 is an apocalyptic number.

It is an amenable number.

643571261 is a deficient number, since it is larger than the sum of its proper divisors (37857151).

643571261 is a wasteful number, since it uses less digits than its factorization.

643571261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37857150.

The product of its digits is 30240, while the sum is 35.

The square root of 643571261 is about 25368.7063328030. The cubic root of 643571261 is about 863.3738305152.

The spelling of 643571261 in words is "six hundred forty-three million, five hundred seventy-one thousand, two hundred sixty-one".