644265533 has 4 divisors (see below), whose sum is σ = 644555520. Its totient is φ = 643975548.

The previous prime is 644265527. The next prime is 644265553. The reversal of 644265533 is 335562446.

It is a happy number.

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, and also an emirpimes, since its reverse is a distinct semiprime: 335562446 = 2 ⋅167781223.

It is a cyclic number.

It is not a de Polignac number, because 644265533 - 2⁸ = 644265277 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644265553) 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 3 ways as a sum of consecutive naturals, for example, 141635 + ... + 146112.

It is an arithmetic number, because the mean of its divisors is an integer number (161138880).

Almost surely, 2^644265533 is an apocalyptic number.

It is an amenable number.

644265533 is a deficient number, since it is larger than the sum of its proper divisors (289987).

644265533 is a wasteful number, since it uses less digits than its factorization.

644265533 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 289986.

The product of its digits is 259200, while the sum is 38.

The square root of 644265533 is about 25382.3862747378. The cubic root of 644265533 is about 863.6841825023.

The spelling of 644265533 in words is "six hundred forty-four million, two hundred sixty-five thousand, five hundred thirty-three".