643777065 has 20 divisors (see below), whose sum is σ = 1154030724. Its totient is φ = 343347552.

The previous prime is 643777051. The next prime is 643777067. The reversal of 643777065 is 560777346.

It can be written as a sum of positive squares in 2 ways, for example, as 178382736 + 465394329 = 13356^2 + 21573^2 .

It is not a de Polignac number, because 643777065 - 2⁴ = 643777049 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 643777065.

It is not an unprimeable number, because it can be changed into a prime (643777067) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 794382 + ... + 795191.

Almost surely, 2^643777065 is an apocalyptic number.

It is an amenable number.

643777065 is a deficient number, since it is larger than the sum of its proper divisors (510253659).

643777065 is a wasteful number, since it uses less digits than its factorization.

643777065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1589590 (or 1589581 counting only the distinct ones).

The product of its (nonzero) digits is 740880, while the sum is 45.

The square root of 643777065 is about 25372.7622658630. The cubic root of 643777065 is about 863.4658518455.

The spelling of 643777065 in words is "six hundred forty-three million, seven hundred seventy-seven thousand, sixty-five".