644742697 has 8 divisors (see below), whose sum is σ = 685211400. Its totient is φ = 604556544.

The previous prime is 644742677. The next prime is 644742719. The reversal of 644742697 is 796247446.

It can be written as a sum of positive squares in 4 ways, for example, as 37810201 + 606932496 = 6149^2 + 24636^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 644742697 - 2¹⁵ = 644709929 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644742697.

It is not an unprimeable number, because it can be changed into a prime (644742677) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 65922 + ... + 75067.

It is an arithmetic number, because the mean of its divisors is an integer number (85651425).

Almost surely, 2^644742697 is an apocalyptic number.

It is an amenable number.

644742697 is a deficient number, since it is larger than the sum of its proper divisors (40468703).

644742697 is a wasteful number, since it uses less digits than its factorization.

644742697 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 141275.

The product of its digits is 2032128, while the sum is 49.

The square root of 644742697 is about 25391.7840452379. The cubic root of 644742697 is about 863.8973540788.

The spelling of 644742697 in words is "six hundred forty-four million, seven hundred forty-two thousand, six hundred ninety-seven".