644995811 has 2 divisors, whose sum is σ = 644995812. Its totient is φ = 644995810.

The previous prime is 644995783. The next prime is 644995823. The reversal of 644995811 is 118599446.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644995811 - 2¹⁸ = 644733667 is a prime.

It is a super-3 number, since 3×644995811³ (a number of 27 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (644995511) 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, 322497905 + 322497906.

It is an arithmetic number, because the mean of its divisors is an integer number (322497906).

Almost surely, 2^644995811 is an apocalyptic number.

644995811 is a deficient number, since it is larger than the sum of its proper divisors (1).

644995811 is an equidigital number, since it uses as much as digits as its factorization.

644995811 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 311040, while the sum is 47.

The square root of 644995811 is about 25396.7677274097. The cubic root of 644995811 is about 864.0103893034.

The spelling of 644995811 in words is "six hundred forty-four million, nine hundred ninety-five thousand, eight hundred eleven".