644774487778 has 8 divisors (see below), whose sum is σ = 967369157568. Its totient is φ = 322318101924.

The previous prime is 644774487761. The next prime is 644774487787. The reversal of 644774487778 is 877784477446.

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

It is a self number, because there is not a number n which added to its sum of digits gives 644774487778.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 34559326 + ... + 34577977.

It is an arithmetic number, because the mean of its divisors is an integer number (120921144696).

Almost surely, 2^644774487778 is an apocalyptic number.

644774487778 is a deficient number, since it is larger than the sum of its proper divisors (322594669790).

644774487778 is a wasteful number, since it uses less digits than its factorization.

644774487778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69141968.

The product of its digits is 1652195328, while the sum is 73.

The spelling of 644774487778 in words is "six hundred forty-four billion, seven hundred seventy-four million, four hundred eighty-seven thousand, seven hundred seventy-eight".