644666453 has 4 divisors (see below), whose sum is σ = 647045568. Its totient is φ = 642287340.

The previous prime is 644666443. The next prime is 644666459. The reversal of 644666453 is 354666446.

It is a happy number.

644666453 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 354666446 = 2 ⋅177333223.

It is a cyclic number.

It is not a de Polignac number, because 644666453 - 2⁴ = 644666437 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644666459) 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, 1189151 + ... + 1189692.

It is an arithmetic number, because the mean of its divisors is an integer number (161761392).

Almost surely, 2^644666453 is an apocalyptic number.

It is an amenable number.

644666453 is a deficient number, since it is larger than the sum of its proper divisors (2379115).

644666453 is a wasteful number, since it uses less digits than its factorization.

644666453 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2379114.

The product of its digits is 1244160, while the sum is 44.

The square root of 644666453 is about 25390.2826490766. The cubic root of 644666453 is about 863.8632993638.

The spelling of 644666453 in words is "six hundred forty-four million, six hundred sixty-six thousand, four hundred fifty-three".