645057809 has 16 divisors (see below), whose sum is σ = 784313280. Its totient is φ = 522869760.

The previous prime is 645057781. The next prime is 645057821. The reversal of 645057809 is 908750546.

It is a cyclic number.

It is not a de Polignac number, because 645057809 - 2¹⁶ = 644992273 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 645057809.

It is not an unprimeable number, because it can be changed into a prime (645057869) 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, 87224 + ... + 94329.

It is an arithmetic number, because the mean of its divisors is an integer number (49019580).

Almost surely, 2^645057809 is an apocalyptic number.

It is an amenable number.

645057809 is a deficient number, since it is larger than the sum of its proper divisors (139255471).

645057809 is a wasteful number, since it uses less digits than its factorization.

645057809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 181600.

The product of its (nonzero) digits is 302400, while the sum is 44.

The square root of 645057809 is about 25397.9882864765. The cubic root of 645057809 is about 864.0380717570.

The spelling of 645057809 in words is "six hundred forty-five million, fifty-seven thousand, eight hundred nine".