645865853 has 4 divisors (see below), whose sum is σ = 683857980. Its totient is φ = 607873728.

The previous prime is 645865789. The next prime is 645865859. The reversal of 645865853 is 358568546.

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 227949604 + 417916249 = 15098^2 + 20443^2 .

It is a cyclic number.

It is not a de Polignac number, because 645865853 - 2⁶ = 645865789 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645865859) 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, 18996038 + ... + 18996071.

It is an arithmetic number, because the mean of its divisors is an integer number (170964495).

Almost surely, 2^645865853 is an apocalyptic number.

It is an amenable number.

645865853 is a deficient number, since it is larger than the sum of its proper divisors (37992127).

645865853 is a wasteful number, since it uses less digits than its factorization.

645865853 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37992126.

The product of its digits is 3456000, while the sum is 50.

The square root of 645865853 is about 25413.8909457013. The cubic root of 645865853 is about 864.3987058184.

The spelling of 645865853 in words is "six hundred forty-five million, eight hundred sixty-five thousand, eight hundred fifty-three".