644340533 has 4 divisors (see below), whose sum is σ = 661755180. Its totient is φ = 626925888.

The previous prime is 644340497. The next prime is 644340539. The reversal of 644340533 is 335043446.

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 621853969 + 22486564 = 24937^2 + 4742^2 .

It is a cyclic number.

It is not a de Polignac number, because 644340533 - 2¹² = 644336437 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644340533.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644340539) 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, 8707268 + ... + 8707341.

It is an arithmetic number, because the mean of its divisors is an integer number (165438795).

Almost surely, 2^644340533 is an apocalyptic number.

It is an amenable number.

644340533 is a deficient number, since it is larger than the sum of its proper divisors (17414647).

644340533 is a wasteful number, since it uses less digits than its factorization.

644340533 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17414646.

The product of its (nonzero) digits is 51840, while the sum is 32.

The square root of 644340533 is about 25383.8636342067. The cubic root of 644340533 is about 863.7176954960.

Adding to 644340533 its reverse (335043446), we get a palindrome (979383979).

The spelling of 644340533 in words is "six hundred forty-four million, three hundred forty thousand, five hundred thirty-three".