644242541 has 2 divisors, whose sum is σ = 644242542. Its totient is φ = 644242540.

The previous prime is 644242537. The next prime is 644242559. The reversal of 644242541 is 145242446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 529966441 + 114276100 = 23021^2 + 10690^2 .

It is a cyclic number.

It is not a de Polignac number, because 644242541 - 2² = 644242537 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 644242498 and 644242507.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644242561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322121270 + 322121271.

It is an arithmetic number, because the mean of its divisors is an integer number (322121271).

Almost surely, 2^644242541 is an apocalyptic number.

It is an amenable number.

644242541 is a deficient number, since it is larger than the sum of its proper divisors (1).

644242541 is an equidigital number, since it uses as much as digits as its factorization.

644242541 is an evil number, because the sum of its binary digits is even.

The product of its digits is 30720, while the sum is 32.

The square root of 644242541 is about 25381.9333581979. The cubic root of 644242541 is about 863.6739082380.

Adding to 644242541 its reverse (145242446), we get a palindrome (789484987).

The spelling of 644242541 in words is "six hundred forty-four million, two hundred forty-two thousand, five hundred forty-one".