645863779 has 16 divisors (see below), whose sum is σ = 747895680. Its totient is φ = 551224960.

The previous prime is 645863767. The next prime is 645863797. The reversal of 645863779 is 977368546.

It is a happy number.

It is a de Polignac number, because none of the positive numbers 2^k-645863779 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645861779) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 74232 + ... + 82474.

It is an arithmetic number, because the mean of its divisors is an integer number (46743480).

Almost surely, 2^645863779 is an apocalyptic number.

645863779 is a deficient number, since it is larger than the sum of its proper divisors (102031901).

645863779 is a wasteful number, since it uses less digits than its factorization.

645863779 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8690.

The product of its digits is 7620480, while the sum is 55.

The square root of 645863779 is about 25413.8501412124. The cubic root of 645863779 is about 864.3977805670.

The spelling of 645863779 in words is "six hundred forty-five million, eight hundred sixty-three thousand, seven hundred seventy-nine".