644563409 has 4 divisors (see below), whose sum is σ = 736643904. Its totient is φ = 552482916.

The previous prime is 644563373. The next prime is 644563411. The reversal of 644563409 is 904365446.

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 644563409 - 2¹² = 644559313 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644563459) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 46040237 + ... + 46040250.

It is an arithmetic number, because the mean of its divisors is an integer number (184160976).

Almost surely, 2^644563409 is an apocalyptic number.

It is an amenable number.

644563409 is a deficient number, since it is larger than the sum of its proper divisors (92080495).

644563409 is an equidigital number, since it uses as much as digits as its factorization.

644563409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 92080494.

The product of its (nonzero) digits is 311040, while the sum is 41.

The square root of 644563409 is about 25388.2533664685. The cubic root of 644563409 is about 863.8172700450.

The spelling of 644563409 in words is "six hundred forty-four million, five hundred sixty-three thousand, four hundred nine".