644170561 has 2 divisors, whose sum is σ = 644170562. Its totient is φ = 644170560.

The previous prime is 644170531. The next prime is 644170651. The reversal of 644170561 is 165071446.

Together with next prime (644170651) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 329640336 + 314530225 = 18156^2 + 17735^2 .

It is a cyclic number.

It is not a de Polignac number, because 644170561 - 2¹³ = 644162369 is a prime.

It is not a weakly prime, because it can be changed into another prime (644170531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322085280 + 322085281.

It is an arithmetic number, because the mean of its divisors is an integer number (322085281).

Almost surely, 2^644170561 is an apocalyptic number.

It is an amenable number.

644170561 is a deficient number, since it is larger than the sum of its proper divisors (1).

644170561 is an equidigital number, since it uses as much as digits as its factorization.

644170561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20160, while the sum is 34.

The square root of 644170561 is about 25380.5153808980. The cubic root of 644170561 is about 863.6417414896.

The spelling of 644170561 in words is "six hundred forty-four million, one hundred seventy thousand, five hundred sixty-one".