645839993 has 2 divisors, whose sum is σ = 645839994. Its totient is φ = 645839992.

The previous prime is 645839989. The next prime is 645840007. The reversal of 645839993 is 399938546.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 645566464 + 273529 = 25408^2 + 523^2 .

It is a cyclic number.

It is not a de Polignac number, because 645839993 - 2² = 645839989 is a prime.

It is not a weakly prime, because it can be changed into another prime (645839903) 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 as a sum of consecutive naturals, namely, 322919996 + 322919997.

It is an arithmetic number, because the mean of its divisors is an integer number (322919997).

Almost surely, 2^645839993 is an apocalyptic number.

It is an amenable number.

645839993 is a deficient number, since it is larger than the sum of its proper divisors (1).

645839993 is an equidigital number, since it uses as much as digits as its factorization.

645839993 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6298560, while the sum is 56.

The square root of 645839993 is about 25413.3821637341. The cubic root of 645839993 is about 864.3871690322.

The spelling of 645839993 in words is "six hundred forty-five million, eight hundred thirty-nine thousand, nine hundred ninety-three".