644143243 has 4 divisors (see below), whose sum is σ = 682034040. Its totient is φ = 606252448.

The previous prime is 644143217. The next prime is 644143259. The reversal of 644143243 is 342341446.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 644143243 - 2²¹ = 642046091 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644143043) 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, 18945373 + ... + 18945406.

It is an arithmetic number, because the mean of its divisors is an integer number (170508510).

Almost surely, 2^644143243 is an apocalyptic number.

644143243 is a deficient number, since it is larger than the sum of its proper divisors (37890797).

644143243 is a wasteful number, since it uses less digits than its factorization.

644143243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37890796.

The product of its digits is 27648, while the sum is 31.

The square root of 644143243 is about 25379.9772064515. The cubic root of 644143243 is about 863.6295328707.

Adding to 644143243 its reverse (342341446), we get a palindrome (986484689).

The spelling of 644143243 in words is "six hundred forty-four million, one hundred forty-three thousand, two hundred forty-three".