645291865 has 16 divisors (see below), whose sum is σ = 822138768. Its totient is φ = 484540416.

The previous prime is 645291863. The next prime is 645291901. The reversal of 645291865 is 568192546.

It can be written as a sum of positive squares in 8 ways, for example, as 741321 + 644550544 = 861^2 + 25388^2 .

It is a cyclic number.

It is not a de Polignac number, because 645291865 - 2¹ = 645291863 is a prime.

It is not an unprimeable number, because it can be changed into a prime (645291863) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21529 + ... + 41881.

It is an arithmetic number, because the mean of its divisors is an integer number (51383673).

Almost surely, 2^645291865 is an apocalyptic number.

It is an amenable number.

645291865 is a deficient number, since it is larger than the sum of its proper divisors (176846903).

645291865 is a wasteful number, since it uses less digits than its factorization.

645291865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20748.

The product of its digits is 518400, while the sum is 46.

The square root of 645291865 is about 25402.5956350921. The cubic root of 645291865 is about 864.1425630844.

The spelling of 645291865 in words is "six hundred forty-five million, two hundred ninety-one thousand, eight hundred sixty-five".