644157693 has 24 divisors (see below), whose sum is σ = 1001894400. Its totient is φ = 397321344.

The previous prime is 644157691. The next prime is 644157721. The reversal of 644157693 is 396751446.

644157693 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 644157693 - 2¹ = 644157691 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644157691) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 26653 + ... + 44706.

It is an arithmetic number, because the mean of its divisors is an integer number (41745600).

Almost surely, 2^644157693 is an apocalyptic number.

It is an amenable number.

644157693 is a deficient number, since it is larger than the sum of its proper divisors (357736707).

644157693 is a wasteful number, since it uses less digits than its factorization.

644157693 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 71441 (or 71438 counting only the distinct ones).

The product of its digits is 544320, while the sum is 45.

The square root of 644157693 is about 25380.2618780816. The cubic root of 644157693 is about 863.6359907269.

The spelling of 644157693 in words is "six hundred forty-four million, one hundred fifty-seven thousand, six hundred ninety-three".