644735715687668 has 48 divisors (see below), whose sum is σ = 1257056301441024. Its totient is φ = 286824344982240.

The previous prime is 644735715687647. The next prime is 644735715687683. The reversal of 644735715687668 is 866786517537446.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 320328821 + ... + 322335267.

It is an arithmetic number, because the mean of its divisors is an integer number (26188672946688).

Almost surely, 2^{644735715687668} is an apocalyptic number.

It is an amenable number.

644735715687668 is a deficient number, since it is larger than the sum of its proper divisors (612320585753356).

644735715687668 is a wasteful number, since it uses less digits than its factorization.

644735715687668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2161892 (or 2161890 counting only the distinct ones).

The product of its digits is 34139750400, while the sum is 83.

The spelling of 644735715687668 in words is "six hundred forty-four trillion, seven hundred thirty-five billion, seven hundred fifteen million, six hundred eighty-seven thousand, six hundred sixty-eight".