644406621 has 8 divisors (see below), whose sum is σ = 861194880. Its totient is φ = 428611392.

The previous prime is 644406619. The next prime is 644406629. The reversal of 644406621 is 126604446.

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

It is not a de Polignac number, because 644406621 - 2¹ = 644406619 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644406629) 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, 246741 + ... + 249338.

It is an arithmetic number, because the mean of its divisors is an integer number (107649360).

Almost surely, 2^644406621 is an apocalyptic number.

It is an amenable number.

644406621 is a deficient number, since it is larger than the sum of its proper divisors (216788259).

644406621 is a wasteful number, since it uses less digits than its factorization.

644406621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 496515.

The product of its (nonzero) digits is 27648, while the sum is 33.

The square root of 644406621 is about 25385.1653727133. The cubic root of 644406621 is about 863.7472240970.

The spelling of 644406621 in words is "six hundred forty-four million, four hundred six thousand, six hundred twenty-one".