644216987 has 2 divisors, whose sum is σ = 644216988. Its totient is φ = 644216986.

The previous prime is 644216981. The next prime is 644217011. The reversal of 644216987 is 789612446.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644216987 - 2¹⁰ = 644215963 is a prime.

It is not a weakly prime, because it can be changed into another prime (644216981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322108493 + 322108494.

It is an arithmetic number, because the mean of its divisors is an integer number (322108494).

Almost surely, 2^644216987 is an apocalyptic number.

644216987 is a deficient number, since it is larger than the sum of its proper divisors (1).

644216987 is an equidigital number, since it uses as much as digits as its factorization.

644216987 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 580608, while the sum is 47.

The square root of 644216987 is about 25381.4299636565. The cubic root of 644216987 is about 863.6624888251.

The spelling of 644216987 in words is "six hundred forty-four million, two hundred sixteen thousand, nine hundred eighty-seven".