644140242 has 96 divisors (see below), whose sum is σ = 1527413760. Its totient is φ = 201178080.

The previous prime is 644140213. The next prime is 644140243. The reversal of 644140242 is 242041446.

It is a happy number.

644140242 is a `hidden beast` number, since 6 + 4 + 414 + 0 + 242 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (644140243) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 3372367 + ... + 3372557.

It is an arithmetic number, because the mean of its divisors is an integer number (15910560).

Almost surely, 2^644140242 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644140242, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (763706880).

644140242 is an abundant number, since it is smaller than the sum of its proper divisors (883273518).

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

644140242 is a wasteful number, since it uses less digits than its factorization.

644140242 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 413 (or 388 counting only the distinct ones).

The product of its (nonzero) digits is 6144, while the sum is 27.

The square root of 644140242 is about 25379.9180849742. The cubic root of 644140242 is about 863.6281916803.

Adding to 644140242 its reverse (242041446), we get a palindrome (886181688).

It can be divided in two parts, 6441402 and 42, that added together give a square (6441444 = 2538²).

The spelling of 644140242 in words is "six hundred forty-four million, one hundred forty thousand, two hundred forty-two".