644633641 has 2 divisors, whose sum is σ = 644633642. Its totient is φ = 644633640.

The previous prime is 644633629. The next prime is 644633657. The reversal of 644633641 is 146336446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 606193641 + 38440000 = 24621^2 + 6200^2 .

It is a cyclic number.

It is not a de Polignac number, because 644633641 - 2¹¹ = 644631593 is a prime.

It is a super-4 number, since 4×644633641⁴ (a number of 36 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is a self number, because there is not a number n which added to its sum of digits gives 644633641.

It is not a weakly prime, because it can be changed into another prime (644633681) 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, 322316820 + 322316821.

It is an arithmetic number, because the mean of its divisors is an integer number (322316821).

Almost surely, 2^644633641 is an apocalyptic number.

It is an amenable number.

644633641 is a deficient number, since it is larger than the sum of its proper divisors (1).

644633641 is an equidigital number, since it uses as much as digits as its factorization.

644633641 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 124416, while the sum is 37.

The square root of 644633641 is about 25389.6364881422. The cubic root of 644633641 is about 863.8486429146.

The spelling of 644633641 in words is "six hundred forty-four million, six hundred thirty-three thousand, six hundred forty-one".