644620687 has 2 divisors, whose sum is σ = 644620688. Its totient is φ = 644620686.

The previous prime is 644620649. The next prime is 644620693. The reversal of 644620687 is 786026446.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644620687 - 2¹⁵ = 644587919 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644620987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322310343 + 322310344.

It is an arithmetic number, because the mean of its divisors is an integer number (322310344).

Almost surely, 2^644620687 is an apocalyptic number.

644620687 is a deficient number, since it is larger than the sum of its proper divisors (1).

644620687 is an equidigital number, since it uses as much as digits as its factorization.

644620687 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 387072, while the sum is 43.

The square root of 644620687 is about 25389.3813827750. The cubic root of 644620687 is about 863.8428564908.

The spelling of 644620687 in words is "six hundred forty-four million, six hundred twenty thousand, six hundred eighty-seven".