1638522640 has 20 divisors (see below), whose sum is σ = 3809565324. Its totient is φ = 655409024.

The previous prime is 1638522623. The next prime is 1638522643. The reversal of 1638522640 is 462258361.

It can be written as a sum of positive squares in 2 ways, for example, as 807469056 + 831053584 = 28416^2 + 28828^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a self number, because there is not a number n which added to its sum of digits gives 1638522640.

It is not an unprimeable number, because it can be changed into a prime (1638522643) 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, 10240687 + ... + 10240846.

Almost surely, 2^1638522640 is an apocalyptic number.

1638522640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1638522640 is an abundant number, since it is smaller than the sum of its proper divisors (2171042684).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1638522640 is a wasteful number, since it uses less digits than its factorization.

1638522640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20481546 (or 20481540 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 37.

The square root of 1638522640 is about 40478.6689504485. The cubic root of 1638522640 is about 1178.9194935200.

The spelling of 1638522640 in words is "one billion, six hundred thirty-eight million, five hundred twenty-two thousand, six hundred forty".