644341553 has 2 divisors, whose sum is σ = 644341554. Its totient is φ = 644341552.

The previous prime is 644341549. The next prime is 644341559. The reversal of 644341553 is 355143446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 635443264 + 8898289 = 25208^2 + 2983^2 .

It is a cyclic number.

It is not a de Polignac number, because 644341553 - 2² = 644341549 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (644341559) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322170776 + 322170777.

It is an arithmetic number, because the mean of its divisors is an integer number (322170777).

Almost surely, 2^644341553 is an apocalyptic number.

It is an amenable number.

644341553 is a deficient number, since it is larger than the sum of its proper divisors (1).

644341553 is an equidigital number, since it uses as much as digits as its factorization.

644341553 is an evil number, because the sum of its binary digits is even.

The product of its digits is 86400, while the sum is 35.

The square root of 644341553 is about 25383.8837257028. The cubic root of 644341553 is about 863.7181512548.

Adding to 644341553 its reverse (355143446), we get a palindrome (999484999).

The spelling of 644341553 in words is "six hundred forty-four million, three hundred forty-one thousand, five hundred fifty-three".