644001087 has 4 divisors (see below), whose sum is σ = 858668120. Its totient is φ = 429334056.

The previous prime is 644001079. The next prime is 644001091. The reversal of 644001087 is 780100446.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 644001087 - 2³ = 644001079 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 (644001187) 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 in 3 ways as a sum of consecutive naturals, for example, 107333512 + ... + 107333517.

It is an arithmetic number, because the mean of its divisors is an integer number (214667030).

Almost surely, 2^644001087 is an apocalyptic number.

644001087 is a deficient number, since it is larger than the sum of its proper divisors (214667033).

644001087 is a wasteful number, since it uses less digits than its factorization.

644001087 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214667032.

The product of its (nonzero) digits is 5376, while the sum is 30.

The square root of 644001087 is about 25377.1764977903. The cubic root of 644001087 is about 863.5659967169.

The spelling of 644001087 in words is "six hundred forty-four million, one thousand, eighty-seven".