644961739 has 2 divisors, whose sum is σ = 644961740. Its totient is φ = 644961738.

The previous prime is 644961731. The next prime is 644961749. The reversal of 644961739 is 937169446.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644961739 - 2³ = 644961731 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 644961692 and 644961701.

It is not a weakly prime, because it can be changed into another prime (644961731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322480869 + 322480870.

It is an arithmetic number, because the mean of its divisors is an integer number (322480870).

Almost surely, 2^644961739 is an apocalyptic number.

644961739 is a deficient number, since it is larger than the sum of its proper divisors (1).

644961739 is an equidigital number, since it uses as much as digits as its factorization.

644961739 is an evil number, because the sum of its binary digits is even.

The product of its digits is 979776, while the sum is 49.

The square root of 644961739 is about 25396.0969245276. The cubic root of 644961739 is about 863.9951752095.

The spelling of 644961739 in words is "six hundred forty-four million, nine hundred sixty-one thousand, seven hundred thirty-nine".