644542 has 4 divisors (see below), whose sum is σ = 966816. Its totient is φ = 322270.

The previous prime is 644531. The next prime is 644549. The reversal of 644542 is 245446.

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

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644549) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161134 + ... + 161137.

It is an arithmetic number, because the mean of its divisors is an integer number (241704).

2⁶⁴⁴⁵⁴² is an apocalyptic number.

644542 is a deficient number, since it is larger than the sum of its proper divisors (322274).

644542 is a wasteful number, since it uses less digits than its factorization.

644542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322273.

The product of its digits is 3840, while the sum is 25.

The square root of 644542 is about 802.8337312296. The cubic root of 644542 is about 86.3807706120.

Adding to 644542 its reverse (245446), we get a palindrome (889988).

The spelling of 644542 in words is "six hundred forty-four thousand, five hundred forty-two".