638497765 has 4 divisors (see below), whose sum is σ = 766197324. Its totient is φ = 510798208.

The previous prime is 638497763. The next prime is 638497787. The reversal of 638497765 is 567794836.

It is a happy number.

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 137499076 + 500998689 = 11726^2 + 22383^2 .

It is a cyclic number.

It is not a de Polignac number, because 638497765 - 2¹ = 638497763 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638497763) 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, 63849772 + ... + 63849781.

It is an arithmetic number, because the mean of its divisors is an integer number (191549331).

Almost surely, 2^638497765 is an apocalyptic number.

It is an amenable number.

638497765 is a deficient number, since it is larger than the sum of its proper divisors (127699559).

638497765 is a wasteful number, since it uses less digits than its factorization.

638497765 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127699558.

The product of its digits is 7620480, while the sum is 55.

The square root of 638497765 is about 25268.5133120253. The cubic root of 638497765 is about 861.0990837708.

The spelling of 638497765 in words is "six hundred thirty-eight million, four hundred ninety-seven thousand, seven hundred sixty-five".