638493209 has 8 divisors (see below), whose sum is σ = 646214760. Its totient is φ = 630784000.

The previous prime is 638493199. The next prime is 638493217. The reversal of 638493209 is 902394836.

It can be written as a sum of positive squares in 4 ways, for example, as 294019609 + 344473600 = 17147^2 + 18560^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-638493209 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 638493209.

It is not an unprimeable number, because it can be changed into a prime (638493269) 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, 140249 + ... + 144729.

It is an arithmetic number, because the mean of its divisors is an integer number (80776845).

Almost surely, 2^638493209 is an apocalyptic number.

It is an amenable number.

638493209 is a deficient number, since it is larger than the sum of its proper divisors (7721551).

638493209 is a wasteful number, since it uses less digits than its factorization.

638493209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6171.

The product of its (nonzero) digits is 279936, while the sum is 44.

The square root of 638493209 is about 25268.4231601420. The cubic root of 638493209 is about 861.0970356421.

The spelling of 638493209 in words is "six hundred thirty-eight million, four hundred ninety-three thousand, two hundred nine".