645810909 has 8 divisors (see below), whose sum is σ = 911733120. Its totient is φ = 405214656.

The previous prime is 645810887. The next prime is 645810911. The reversal of 645810909 is 909018546.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 645810909 - 2⁸ = 645810653 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645811909) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6331429 + ... + 6331530.

It is an arithmetic number, because the mean of its divisors is an integer number (113966640).

Almost surely, 2^645810909 is an apocalyptic number.

It is an amenable number.

645810909 is a deficient number, since it is larger than the sum of its proper divisors (265922211).

645810909 is a wasteful number, since it uses less digits than its factorization.

645810909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12662979.

The product of its (nonzero) digits is 77760, while the sum is 42.

The square root of 645810909 is about 25412.8099390839. The cubic root of 645810909 is about 864.3741935718.

The spelling of 645810909 in words is "six hundred forty-five million, eight hundred ten thousand, nine hundred nine".