644748841819 has 4 divisors (see below), whose sum is σ = 650454583896. Its totient is φ = 639043099744.

The previous prime is 644748841783. The next prime is 644748841829. The reversal of 644748841819 is 918148847446.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 644748841819 - 2¹³ = 644748833627 is a prime.

It is a super-2 number, since 2×644748841819² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644748841829) 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 3 ways as a sum of consecutive naturals, for example, 2852870869 + ... + 2852871094.

It is an arithmetic number, because the mean of its divisors is an integer number (162613645974).

Almost surely, 2^644748841819 is an apocalyptic number.

644748841819 is a deficient number, since it is larger than the sum of its proper divisors (5705742077).

644748841819 is a wasteful number, since it uses less digits than its factorization.

644748841819 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5705742076.

The product of its digits is 49545216, while the sum is 64.

The spelling of 644748841819 in words is "six hundred forty-four billion, seven hundred forty-eight million, eight hundred forty-one thousand, eight hundred nineteen".