644906063 has 2 divisors, whose sum is σ = 644906064. Its totient is φ = 644906062.

The previous prime is 644906047. The next prime is 644906081. The reversal of 644906063 is 360609446.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644906063 - 2⁴ = 644906047 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644900063) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322453031 + 322453032.

It is an arithmetic number, because the mean of its divisors is an integer number (322453032).

Almost surely, 2^644906063 is an apocalyptic number.

644906063 is a deficient number, since it is larger than the sum of its proper divisors (1).

644906063 is an equidigital number, since it uses as much as digits as its factorization.

644906063 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 93312, while the sum is 38.

The square root of 644906063 is about 25395.0007481788. Note that the first 3 decimals coincide. The cubic root of 644906063 is about 863.9703131768.

Subtracting from 644906063 its sum of digits (38), we obtain a square (644906025 = 25395²).

The spelling of 644906063 in words is "six hundred forty-four million, nine hundred six thousand, sixty-three".