644774487779 has 16 divisors (see below), whose sum is σ = 663243559776. Its totient is φ = 626437324800.

The previous prime is 644774487761. The next prime is 644774487787. The reversal of 644774487779 is 977784477446.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 644774487779 - 2³⁶ = 576055011043 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644774487179) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 67716539 + ... + 67726059.

It is an arithmetic number, because the mean of its divisors is an integer number (41452722486).

Almost surely, 2^644774487779 is an apocalyptic number.

644774487779 is a deficient number, since it is larger than the sum of its proper divisors (18469071997).

644774487779 is a wasteful number, since it uses less digits than its factorization.

644774487779 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16246.

The product of its digits is 1858719744, while the sum is 74.

The spelling of 644774487779 in words is "six hundred forty-four billion, seven hundred seventy-four million, four hundred eighty-seven thousand, seven hundred seventy-nine".