644433161 has 4 divisors (see below), whose sum is σ = 682341012. Its totient is φ = 606525312.

The previous prime is 644433151. The next prime is 644433187. The reversal of 644433161 is 161334446.

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

It can be written as a sum of positive squares in 2 ways, for example, as 285103225 + 359329936 = 16885^2 + 18956^2 .

It is a cyclic number.

It is not a de Polignac number, because 644433161 - 2¹⁴ = 644416777 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644433151) 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, 18953900 + ... + 18953933.

It is an arithmetic number, because the mean of its divisors is an integer number (170585253).

Almost surely, 2^644433161 is an apocalyptic number.

It is an amenable number.

644433161 is a deficient number, since it is larger than the sum of its proper divisors (37907851).

644433161 is a wasteful number, since it uses less digits than its factorization.

644433161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37907850.

The product of its digits is 20736, while the sum is 32.

The square root of 644433161 is about 25385.6881135808. The cubic root of 644433161 is about 863.7590817947.

The spelling of 644433161 in words is "six hundred forty-four million, four hundred thirty-three thousand, one hundred sixty-one".