644634533 has 4 divisors (see below), whose sum is σ = 666863340. Its totient is φ = 622405728.

The previous prime is 644634517. The next prime is 644634541. The reversal of 644634533 is 335436446.

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 203718529 + 440916004 = 14273^2 + 20998^2 .

It is a cyclic number.

It is not a de Polignac number, because 644634533 - 2⁴ = 644634517 is a prime.

It is a super-2 number, since 2×644634533² = 831107362272256178, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644634583) 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, 11114360 + ... + 11114417.

It is an arithmetic number, because the mean of its divisors is an integer number (166715835).

Almost surely, 2^644634533 is an apocalyptic number.

It is an amenable number.

644634533 is a deficient number, since it is larger than the sum of its proper divisors (22228807).

644634533 is a wasteful number, since it uses less digits than its factorization.

644634533 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22228806.

The product of its digits is 311040, while the sum is 38.

The square root of 644634533 is about 25389.6540543584. The cubic root of 644634533 is about 863.8490413593.

The spelling of 644634533 in words is "six hundred forty-four million, six hundred thirty-four thousand, five hundred thirty-three".