644766643 has 2 divisors, whose sum is σ = 644766644. Its totient is φ = 644766642.

The previous prime is 644766631. The next prime is 644766671. The reversal of 644766643 is 346667446.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644766643 - 2⁵ = 644766611 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 644766593 and 644766602.

It is not a weakly prime, because it can be changed into another prime (644766043) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322383321 + 322383322.

It is an arithmetic number, because the mean of its divisors is an integer number (322383322).

Almost surely, 2^644766643 is an apocalyptic number.

644766643 is a deficient number, since it is larger than the sum of its proper divisors (1).

644766643 is an equidigital number, since it uses as much as digits as its factorization.

644766643 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1741824, while the sum is 46.

The square root of 644766643 is about 25392.2555713351. The cubic root of 644766643 is about 863.9080491101.

The spelling of 644766643 in words is "six hundred forty-four million, seven hundred sixty-six thousand, six hundred forty-three".