644646451 has 2 divisors, whose sum is σ = 644646452. Its totient is φ = 644646450.

The previous prime is 644646439. The next prime is 644646479. The reversal of 644646451 is 154646446.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644646451 - 2¹⁷ = 644515379 is a prime.

It is a super-3 number, since 3×644646451³ (a number of 27 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (644641451) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322323225 + 322323226.

It is an arithmetic number, because the mean of its divisors is an integer number (322323226).

Almost surely, 2^644646451 is an apocalyptic number.

644646451 is a deficient number, since it is larger than the sum of its proper divisors (1).

644646451 is an equidigital number, since it uses as much as digits as its factorization.

644646451 is an evil number, because the sum of its binary digits is even.

The product of its digits is 276480, while the sum is 40.

The square root of 644646451 is about 25389.8887551718. Note that the first 3 decimals coincide. The cubic root of 644646451 is about 863.8543649387.

The spelling of 644646451 in words is "six hundred forty-four million, six hundred forty-six thousand, four hundred fifty-one".