1638481668 has 12 divisors (see below), whose sum is σ = 3823123920. Its totient is φ = 546160552.

The previous prime is 1638481661. The next prime is 1638481679. The reversal of 1638481668 is 8661848361.

It is a tau number, because it is divible by the number of its divisors (12).

It is a self number, because there is not a number n which added to its sum of digits gives 1638481668.

It is not an unprimeable number, because it can be changed into a prime (1638481661) 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, 68270058 + ... + 68270081.

It is an arithmetic number, because the mean of its divisors is an integer number (318593660).

Almost surely, 2^1638481668 is an apocalyptic number.

It is an amenable number.

1638481668 is an abundant number, since it is smaller than the sum of its proper divisors (2184642252).

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

1638481668 is a wasteful number, since it uses less digits than its factorization.

1638481668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 136540146 (or 136540144 counting only the distinct ones).

The product of its digits is 1327104, while the sum is 51.

The square root of 1638481668 is about 40478.1628535683. The cubic root of 1638481668 is about 1178.9096669663.

The spelling of 1638481668 in words is "one billion, six hundred thirty-eight million, four hundred eighty-one thousand, six hundred sixty-eight".