644867242 has 4 divisors (see below), whose sum is σ = 967300866. Its totient is φ = 322433620.

The previous prime is 644867221. The next prime is 644867243. The reversal of 644867242 is 242768446.

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

It can be written as a sum of positive squares in only one way, i.e., 641659561 + 3207681 = 25331^2 + 1791^2 .

It is not an unprimeable number, because it can be changed into a prime (644867243) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161216809 + ... + 161216812.

Almost surely, 2^644867242 is an apocalyptic number.

644867242 is a deficient number, since it is larger than the sum of its proper divisors (322433624).

644867242 is a wasteful number, since it uses less digits than its factorization.

644867242 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322433623.

The product of its digits is 516096, while the sum is 43.

The square root of 644867242 is about 25394.2363933236. The cubic root of 644867242 is about 863.9529768718.

The spelling of 644867242 in words is "six hundred forty-four million, eight hundred sixty-seven thousand, two hundred forty-two".