644978441 has 2 divisors, whose sum is σ = 644978442. Its totient is φ = 644978440.

The previous prime is 644978431. The next prime is 644978447. The reversal of 644978441 is 144879446.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 639078400 + 5900041 = 25280^2 + 2429^2 .

It is a cyclic number.

It is not a de Polignac number, because 644978441 - 2⁶ = 644978377 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (644978447) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322489220 + 322489221.

It is an arithmetic number, because the mean of its divisors is an integer number (322489221).

Almost surely, 2^644978441 is an apocalyptic number.

It is an amenable number.

644978441 is a deficient number, since it is larger than the sum of its proper divisors (1).

644978441 is an equidigital number, since it uses as much as digits as its factorization.

644978441 is an evil number, because the sum of its binary digits is even.

The product of its digits is 774144, while the sum is 47.

The square root of 644978441 is about 25396.4257524558. The cubic root of 644978441 is about 864.0026331831.

The spelling of 644978441 in words is "six hundred forty-four million, nine hundred seventy-eight thousand, four hundred forty-one".