644071533 has 24 divisors (see below), whose sum is σ = 999925920. Its totient is φ = 367688160.

The previous prime is 644071513. The next prime is 644071541. The reversal of 644071533 is 335170446.

It is not a de Polignac number, because 644071533 - 2¹⁸ = 643809389 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 644071494 and 644071503.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644071513) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 282723 + ... + 284991.

It is an arithmetic number, because the mean of its divisors is an integer number (41663580).

Almost surely, 2^644071533 is an apocalyptic number.

It is an amenable number.

644071533 is a deficient number, since it is larger than the sum of its proper divisors (355854387).

644071533 is a wasteful number, since it uses less digits than its factorization.

644071533 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4217 (or 4210 counting only the distinct ones).

The product of its (nonzero) digits is 30240, while the sum is 33.

The square root of 644071533 is about 25378.5644393059. The cubic root of 644071533 is about 863.5974834920.

The spelling of 644071533 in words is "six hundred forty-four million, seventy-one thousand, five hundred thirty-three".