644331220642 has 8 divisors (see below), whose sum is σ = 966528726300. Its totient is φ = 322154978544.

The previous prime is 644331220639. The next prime is 644331220649. The reversal of 644331220642 is 246022133446.

It can be written as a sum of positive squares in 2 ways, for example, as 642609053641 + 1722167001 = 801629^2 + 41499^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (644331220649) 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, 5239917 + ... + 5361472.

Almost surely, 2^644331220642 is an apocalyptic number.

644331220642 is a deficient number, since it is larger than the sum of its proper divisors (322197505658).

644331220642 is a wasteful number, since it uses less digits than its factorization.

644331220642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10631780.

The product of its (nonzero) digits is 165888, while the sum is 37.

The spelling of 644331220642 in words is "six hundred forty-four billion, three hundred thirty-one million, two hundred twenty thousand, six hundred forty-two".