644068653 has 4 divisors (see below), whose sum is σ = 858758208. Its totient is φ = 429379100.

The previous prime is 644068643. The next prime is 644068661. The reversal of 644068653 is 356860446.

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.

It is a cyclic number.

It is not a de Polignac number, because 644068653 - 2⁴ = 644068637 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644068643) 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, 107344773 + ... + 107344778.

It is an arithmetic number, because the mean of its divisors is an integer number (214689552).

Almost surely, 2^644068653 is an apocalyptic number.

It is an amenable number.

644068653 is a deficient number, since it is larger than the sum of its proper divisors (214689555).

644068653 is a wasteful number, since it uses less digits than its factorization.

644068653 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214689554.

The product of its (nonzero) digits is 414720, while the sum is 42.

The square root of 644068653 is about 25378.5076984444. The cubic root of 644068653 is about 863.5961962828.

The spelling of 644068653 in words is "six hundred forty-four million, sixty-eight thousand, six hundred fifty-three".