644404423656654 has 16 divisors (see below), whose sum is σ = 1432009830348240. Its totient is φ = 214801474552200.

The previous prime is 644404423656641. The next prime is 644404423656689. The reversal of 644404423656654 is 456656324404446.

644404423656654 is a `hidden beast` number, since 6 + 4 + 4 + 4 + 0 + 44 + 23 + 6 + 566 + 5 + 4 = 666.

It is a super-2 number, since 2×644404423656654² (a number of 30 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 644404423656591 and 644404423656600.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5966707626397 + ... + 5966707626504.

It is an arithmetic number, because the mean of its divisors is an integer number (89500614396765).

Almost surely, 2^{644404423656654} is an apocalyptic number.

644404423656654 is an abundant number, since it is smaller than the sum of its proper divisors (787605406691586).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644404423656654 is a wasteful number, since it uses less digits than its factorization.

644404423656654 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11933415252912 (or 11933415252906 counting only the distinct ones).

The product of its (nonzero) digits is 796262400, while the sum is 63.

The spelling of 644404423656654 in words is "six hundred forty-four trillion, four hundred four billion, four hundred twenty-three million, six hundred fifty-six thousand, six hundred fifty-four".