645809813 has 8 divisors (see below), whose sum is σ = 705178656. Its totient is φ = 586550800.

The previous prime is 645809777. The next prime is 645809831. The reversal of 645809813 is 318908546.

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

It is not a de Polignac number, because 645809813 - 2¹⁴ = 645793429 is a prime.

It is a super-3 number, since 3×645809813³ (a number of 27 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645809833) 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, 14906 + ... + 38907.

It is an arithmetic number, because the mean of its divisors is an integer number (88147332).

Almost surely, 2^645809813 is an apocalyptic number.

It is an amenable number.

645809813 is a deficient number, since it is larger than the sum of its proper divisors (59368843).

645809813 is a wasteful number, since it uses less digits than its factorization.

645809813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54915.

The product of its (nonzero) digits is 207360, while the sum is 44.

The square root of 645809813 is about 25412.7883751469. The cubic root of 645809813 is about 864.3737045975.

The spelling of 645809813 in words is "six hundred forty-five million, eight hundred nine thousand, eight hundred thirteen".