1638686481 has 4 divisors (see below), whose sum is σ = 2184915312. Its totient is φ = 1092457652.

The previous prime is 1638686479. The next prime is 1638686501. The reversal of 1638686481 is 1846868361.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1638686481 - 2¹ = 1638686479 is a prime.

It is a super-2 number, since 2×1638686481² = 5370586766024326722, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1638686471) 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, 273114411 + ... + 273114416.

It is an arithmetic number, because the mean of its divisors is an integer number (546228828).

Almost surely, 2^1638686481 is an apocalyptic number.

It is an amenable number.

1638686481 is a deficient number, since it is larger than the sum of its proper divisors (546228831).

1638686481 is an equidigital number, since it uses as much as digits as its factorization.

1638686481 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 546228830.

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

The square root of 1638686481 is about 40480.6926941721. The cubic root of 1638686481 is about 1178.9587868253.

The spelling of 1638686481 in words is "one billion, six hundred thirty-eight million, six hundred eighty-six thousand, four hundred eighty-one".