1638649459 has 4 divisors (see below), whose sum is σ = 1642542160. Its totient is φ = 1634756760.

The previous prime is 1638649457. The next prime is 1638649483. The reversal of 1638649459 is 9549468361.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 1638649459 - 2¹ = 1638649457 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1638649457) 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, 1945719 + ... + 1946560.

It is an arithmetic number, because the mean of its divisors is an integer number (410635540).

Almost surely, 2^1638649459 is an apocalyptic number.

1638649459 is a deficient number, since it is larger than the sum of its proper divisors (3892701).

1638649459 is an equidigital number, since it uses as much as digits as its factorization.

1638649459 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3892700.

The product of its digits is 5598720, while the sum is 55.

The square root of 1638649459 is about 40480.2354118649. The cubic root of 1638649459 is about 1178.9499082222.

The spelling of 1638649459 in words is "one billion, six hundred thirty-eight million, six hundred forty-nine thousand, four hundred fifty-nine".