644005243 has 16 divisors (see below), whose sum is σ = 751398336. Its totient is φ = 540541440.

The previous prime is 644005199. The next prime is 644005277. The reversal of 644005243 is 342500446.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644005243 is a prime.

It is a super-2 number, since 2×644005243² = 829485506022978098, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644005283) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 96255 + ... + 102727.

It is an arithmetic number, because the mean of its divisors is an integer number (46962396).

Almost surely, 2^644005243 is an apocalyptic number.

644005243 is a deficient number, since it is larger than the sum of its proper divisors (107393093).

644005243 is a wasteful number, since it uses less digits than its factorization.

644005243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6774.

The product of its (nonzero) digits is 11520, while the sum is 28.

The square root of 644005243 is about 25377.2583822603. The cubic root of 644005243 is about 863.5678543601.

Adding to 644005243 its reverse (342500446), we get a palindrome (986505689).

The spelling of 644005243 in words is "six hundred forty-four million, five thousand, two hundred forty-three".