645730993 has 4 divisors (see below), whose sum is σ = 663183220. Its totient is φ = 628278768.

The previous prime is 645730991. The next prime is 645731011. The reversal of 645730993 is 399037546.

645730993 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 399037546 = 2 ⋅199518773.

It can be written as a sum of positive squares in 2 ways, for example, as 357512464 + 288218529 = 18908^2 + 16977^2 .

It is a cyclic number.

It is not a de Polignac number, because 645730993 - 2¹ = 645730991 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645730991) 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, 8726058 + ... + 8726131.

It is an arithmetic number, because the mean of its divisors is an integer number (165795805).

Almost surely, 2^645730993 is an apocalyptic number.

It is an amenable number.

645730993 is a deficient number, since it is larger than the sum of its proper divisors (17452227).

645730993 is a wasteful number, since it uses less digits than its factorization.

645730993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17452226.

The product of its (nonzero) digits is 612360, while the sum is 46.

The square root of 645730993 is about 25411.2375338156. The cubic root of 645730993 is about 864.3385380485.

The spelling of 645730993 in words is "six hundred forty-five million, seven hundred thirty thousand, nine hundred ninety-three".