638556697 has 4 divisors (see below), whose sum is σ = 639227700. Its totient is φ = 637885696.

The previous prime is 638556679. The next prime is 638556701. The reversal of 638556697 is 796655836.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 359633296 + 278923401 = 18964^2 + 16701^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-638556697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (638550697) 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, 334072 + ... + 335977.

It is an arithmetic number, because the mean of its divisors is an integer number (159806925).

Almost surely, 2^638556697 is an apocalyptic number.

It is an amenable number.

638556697 is a deficient number, since it is larger than the sum of its proper divisors (671003).

638556697 is an equidigital number, since it uses as much as digits as its factorization.

638556697 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 671002.

The product of its digits is 8164800, while the sum is 55.

The square root of 638556697 is about 25269.6794004198. The cubic root of 638556697 is about 861.1255755002.

The spelling of 638556697 in words is "six hundred thirty-eight million, five hundred fifty-six thousand, six hundred ninety-seven".