644335231 has 4 divisors (see below), whose sum is σ = 644389992. Its totient is φ = 644280472.

The previous prime is 644335229. The next prime is 644335261. The reversal of 644335231 is 132533446.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 132533446 = 2 ⋅66266723.

It is a cyclic number.

It is not a de Polignac number, because 644335231 - 2¹ = 644335229 is a prime.

It is a super-2 number, since 2×644335231² = 830335779815646722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 644335193 and 644335202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644335261) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1705 + ... + 35938.

It is an arithmetic number, because the mean of its divisors is an integer number (161097498).

Almost surely, 2^644335231 is an apocalyptic number.

644335231 is a deficient number, since it is larger than the sum of its proper divisors (54761).

644335231 is a wasteful number, since it uses less digits than its factorization.

644335231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54760.

The product of its digits is 25920, while the sum is 31.

The square root of 644335231 is about 25383.7591975657. The cubic root of 644335231 is about 863.7153264362.

Adding to 644335231 its reverse (132533446), we get a palindrome (776868677).

The spelling of 644335231 in words is "six hundred forty-four million, three hundred thirty-five thousand, two hundred thirty-one".