644849638 has 4 divisors (see below), whose sum is σ = 967274460. Its totient is φ = 322424818.

The previous prime is 644849633. The next prime is 644849651. The reversal of 644849638 is 836948446.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 836948446 = 2 ⋅418474223.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644849633) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161212408 + ... + 161212411.

It is an arithmetic number, because the mean of its divisors is an integer number (241818615).

Almost surely, 2^644849638 is an apocalyptic number.

644849638 is a deficient number, since it is larger than the sum of its proper divisors (322424822).

644849638 is a wasteful number, since it uses less digits than its factorization.

644849638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 322424821.

The product of its digits is 3981312, while the sum is 52.

The square root of 644849638 is about 25393.8897768735. The cubic root of 644849638 is about 863.9451152193.

The spelling of 644849638 in words is "six hundred forty-four million, eight hundred forty-nine thousand, six hundred thirty-eight".