644551634501 has 2 divisors, whose sum is σ = 644551634502. Its totient is φ = 644551634500.

The previous prime is 644551634453. The next prime is 644551634633. The reversal of 644551634501 is 105436155446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 554725550401 + 89826084100 = 744799^2 + 299710^2 .

It is a cyclic number.

It is not a de Polignac number, because 644551634501 - 2³⁸ = 369673727557 is a prime.

It is a super-3 number, since 3×644551634501³ (a number of 36 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644551634401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322275817250 + 322275817251.

It is an arithmetic number, because the mean of its divisors is an integer number (322275817251).

Almost surely, 2^644551634501 is an apocalyptic number.

It is an amenable number.

644551634501 is a deficient number, since it is larger than the sum of its proper divisors (1).

644551634501 is an equidigital number, since it uses as much as digits as its factorization.

644551634501 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 864000, while the sum is 44.

Adding to 644551634501 its reverse (105436155446), we get a palindrome (749987789947).

The spelling of 644551634501 in words is "six hundred forty-four billion, five hundred fifty-one million, six hundred thirty-four thousand, five hundred one".