645291993 has 8 divisors (see below), whose sum is σ = 861485728. Its totient is φ = 429646464.

The previous prime is 645291991. The next prime is 645292019. The reversal of 645291993 is 399192546.

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

It is not a de Polignac number, because 645291993 - 2¹ = 645291991 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645291991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 134296 + ... + 139017.

It is an arithmetic number, because the mean of its divisors is an integer number (107685716).

Almost surely, 2^645291993 is an apocalyptic number.

It is an amenable number.

645291993 is a deficient number, since it is larger than the sum of its proper divisors (216193735).

645291993 is a wasteful number, since it uses less digits than its factorization.

645291993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 274103.

The product of its digits is 524880, while the sum is 48.

The square root of 645291993 is about 25402.5981545195. The cubic root of 645291993 is about 864.1426202214.

The spelling of 645291993 in words is "six hundred forty-five million, two hundred ninety-one thousand, nine hundred ninety-three".