638666613 has 20 divisors (see below), whose sum is σ = 1027448268. Its totient is φ = 393024960.

The previous prime is 638666603. The next prime is 638666647. The reversal of 638666613 is 316666836.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 31438449 + 607228164 = 5607^2 + 24642^2 .

It is not a de Polignac number, because 638666613 - 2⁶ = 638666549 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638666603) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 302208 + ... + 304313.

Almost surely, 2^638666613 is an apocalyptic number.

It is an amenable number.

638666613 is a deficient number, since it is larger than the sum of its proper divisors (388781655).

638666613 is a wasteful number, since it uses less digits than its factorization.

638666613 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 606546 (or 606537 counting only the distinct ones).

The product of its digits is 559872, while the sum is 45.

The square root of 638666613 is about 25271.8541662459. The cubic root of 638666613 is about 861.1749817361.

The spelling of 638666613 in words is "six hundred thirty-eight million, six hundred sixty-six thousand, six hundred thirteen".