644805997 has 4 divisors (see below), whose sum is σ = 703424736. Its totient is φ = 586187260.

The previous prime is 644805991. The next prime is 644806009. The reversal of 644805997 is 799508446.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 644805997 - 2¹¹ = 644803949 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644805991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 29309353 + ... + 29309374.

It is an arithmetic number, because the mean of its divisors is an integer number (175856184).

Almost surely, 2^644805997 is an apocalyptic number.

It is an amenable number.

644805997 is a deficient number, since it is larger than the sum of its proper divisors (58618739).

644805997 is a wasteful number, since it uses less digits than its factorization.

644805997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58618738.

The product of its (nonzero) digits is 2177280, while the sum is 52.

The square root of 644805997 is about 25393.0304808229. The cubic root of 644805997 is about 863.9256252601.

The spelling of 644805997 in words is "six hundred forty-four million, eight hundred five thousand, nine hundred ninety-seven".