644676537 has 4 divisors (see below), whose sum is σ = 859568720. Its totient is φ = 429784356.

The previous prime is 644676509. The next prime is 644676541. The reversal of 644676537 is 735676446.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 644676537 - 2⁸ = 644676281 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644676337) 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, 107446087 + ... + 107446092.

It is an arithmetic number, because the mean of its divisors is an integer number (214892180).

Almost surely, 2^644676537 is an apocalyptic number.

It is an amenable number.

644676537 is a deficient number, since it is larger than the sum of its proper divisors (214892183).

644676537 is a wasteful number, since it uses less digits than its factorization.

644676537 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214892182.

The product of its digits is 2540160, while the sum is 48.

The square root of 644676537 is about 25390.4812282083. The cubic root of 644676537 is about 863.8678035805.

Subtracting 644676537 from its reverse (735676446), we obtain a palindrome (90999909).

The spelling of 644676537 in words is "six hundred forty-four million, six hundred seventy-six thousand, five hundred thirty-seven".