644221453 has 2 divisors, whose sum is σ = 644221454. Its totient is φ = 644221452.

The previous prime is 644221439. The next prime is 644221499. The reversal of 644221453 is 354122446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 592338244 + 51883209 = 24338^2 + 7203^2 .

It is a cyclic number.

It is not a de Polignac number, because 644221453 - 2¹³ = 644213261 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644251453) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322110726 + 322110727.

It is an arithmetic number, because the mean of its divisors is an integer number (322110727).

Almost surely, 2^644221453 is an apocalyptic number.

It is an amenable number.

644221453 is a deficient number, since it is larger than the sum of its proper divisors (1).

644221453 is an equidigital number, since it uses as much as digits as its factorization.

644221453 is an evil number, because the sum of its binary digits is even.

The product of its digits is 23040, while the sum is 31.

The square root of 644221453 is about 25381.5179412107. The cubic root of 644221453 is about 863.6644845852.

Adding to 644221453 its reverse (354122446), we get a palindrome (998343899).

The spelling of 644221453 in words is "six hundred forty-four million, two hundred twenty-one thousand, four hundred fifty-three".