644136 has 16 divisors (see below), whose sum is σ = 1610400. Its totient is φ = 214704.

The previous prime is 644131. The next prime is 644141. The reversal of 644136 is 631446.

It is an interprime number because it is at equal distance from previous prime (644131) and next prime (644141).

It is a super-2 number, since 2×644136² = 829822372992, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (24), and also a Moran number because the ratio is a prime number: 26839 = 644136 / (6 + 4 + 4 + 1 + 3 + 6).

It is a nude number because it is divisible by every one of its digits.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 644136.

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, 13396 + ... + 13443.

It is an arithmetic number, because the mean of its divisors is an integer number (100650).

2⁶⁴⁴¹³⁶ is an apocalyptic number.

It is an amenable number.

644136 is an abundant number, since it is smaller than the sum of its proper divisors (966264).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644136 is a wasteful number, since it uses less digits than its factorization.

644136 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26848 (or 26844 counting only the distinct ones).

The product of its digits is 1728, while the sum is 24.

The square root of 644136 is about 802.5808370501. The cubic root of 644136 is about 86.3626295862.

It can be divided in two parts, 644 and 136, that added together give a triangular number (780 = T₃₉).

The spelling of 644136 in words is "six hundred forty-four thousand, one hundred thirty-six".