644603478221 has 8 divisors (see below), whose sum is σ = 652807478400. Its totient is φ = 636400589760.

The previous prime is 644603478191. The next prime is 644603478223. The reversal of 644603478221 is 122874306446.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 644603478221 - 2²⁶ = 644536369357 is a prime.

It is a super-2 number, since 2×644603478221² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644603478223) 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 7 ways as a sum of consecutive naturals, for example, 921845 + ... + 1462533.

It is an arithmetic number, because the mean of its divisors is an integer number (81600934800).

Almost surely, 2^644603478221 is an apocalyptic number.

It is an amenable number.

644603478221 is a deficient number, since it is larger than the sum of its proper divisors (8204000179).

644603478221 is a wasteful number, since it uses less digits than its factorization.

644603478221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 555859.

The product of its (nonzero) digits is 1548288, while the sum is 47.

The spelling of 644603478221 in words is "six hundred forty-four billion, six hundred three million, four hundred seventy-eight thousand, two hundred twenty-one".