644137 has 4 divisors (see below), whose sum is σ = 693700. Its totient is φ = 594576.

The previous prime is 644131. The next prime is 644141. The reversal of 644137 is 731446.

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

It can be written as a sum of positive squares in 2 ways, for example, as 318096 + 326041 = 564^2 + 571^2 .

It is a cyclic number.

It is not a de Polignac number, because 644137 - 2³ = 644129 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644131) 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, 24762 + ... + 24787.

It is an arithmetic number, because the mean of its divisors is an integer number (173425).

2⁶⁴⁴¹³⁷ is an apocalyptic number.

It is an amenable number.

644137 is a deficient number, since it is larger than the sum of its proper divisors (49563).

644137 is a wasteful number, since it uses less digits than its factorization.

644137 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49562.

The product of its digits is 2016, while the sum is 25.

The square root of 644137 is about 802.5814600400. The cubic root of 644137 is about 86.3626742779.

The spelling of 644137 in words is "six hundred forty-four thousand, one hundred thirty-seven".