645143123561 has 2 divisors, whose sum is σ = 645143123562. Its totient is φ = 645143123560.

The previous prime is 645143123543. The next prime is 645143123591. The reversal of 645143123561 is 165321341546.

645143123561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 639750424336 + 5392699225 = 799844^2 + 73435^2 .

It is a cyclic number.

It is not a de Polignac number, because 645143123561 - 2¹⁰ = 645143122537 is a prime.

It is not a weakly prime, because it can be changed into another prime (645143123591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322571561780 + 322571561781.

It is an arithmetic number, because the mean of its divisors is an integer number (322571561781).

Almost surely, 2^645143123561 is an apocalyptic number.

It is an amenable number.

645143123561 is a deficient number, since it is larger than the sum of its proper divisors (1).

645143123561 is an equidigital number, since it uses as much as digits as its factorization.

645143123561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 259200, while the sum is 41.

The spelling of 645143123561 in words is "six hundred forty-five billion, one hundred forty-three million, one hundred twenty-three thousand, five hundred sixty-one".