638725989 has 32 divisors (see below), whose sum is σ = 990904320. Its totient is φ = 361670400.

The previous prime is 638725987. The next prime is 638725993. The reversal of 638725989 is 989527836.

It is not a de Polignac number, because 638725989 - 2¹ = 638725987 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638725987) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 73884 + ... + 82074.

It is an arithmetic number, because the mean of its divisors is an integer number (30965760).

Almost surely, 2^638725989 is an apocalyptic number.

It is an amenable number.

638725989 is a deficient number, since it is larger than the sum of its proper divisors (352178331).

638725989 is a wasteful number, since it uses less digits than its factorization.

638725989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8361.

The product of its digits is 6531840, while the sum is 57.

The square root of 638725989 is about 25273.0288845639. The cubic root of 638725989 is about 861.2016683465.

It can be divided in two parts, 638 and 725989, that added together give a palindrome (726627).

The spelling of 638725989 in words is "six hundred thirty-eight million, seven hundred twenty-five thousand, nine hundred eighty-nine".