643744281617 has 2 divisors, whose sum is σ = 643744281618. Its totient is φ = 643744281616.

The previous prime is 643744281571. The next prime is 643744281629. The reversal of 643744281617 is 716182447346.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 627637879696 + 16106401921 = 792236^2 + 126911^2 .

It is a cyclic number.

It is not a de Polignac number, because 643744281617 - 2²⁰ = 643743233041 is a prime.

It is a super-2 number, since 2×643744281617² (a number of 24 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (643744281637) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321872140808 + 321872140809.

It is an arithmetic number, because the mean of its divisors is an integer number (321872140809).

Almost surely, 2^643744281617 is an apocalyptic number.

It is an amenable number.

643744281617 is a deficient number, since it is larger than the sum of its proper divisors (1).

643744281617 is an equidigital number, since it uses as much as digits as its factorization.

643744281617 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5419008, while the sum is 53.

The spelling of 643744281617 in words is "six hundred forty-three billion, seven hundred forty-four million, two hundred eighty-one thousand, six hundred seventeen".