1638543694 has 4 divisors (see below), whose sum is σ = 2457815544. Its totient is φ = 819271846.

The previous prime is 1638543671. The next prime is 1638543737. The reversal of 1638543694 is 4963458361.

It is a happy number.

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

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an alternating number because its digits alternate between odd and even.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 409635922 + ... + 409635925.

It is an arithmetic number, because the mean of its divisors is an integer number (614453886).

Almost surely, 2^1638543694 is an apocalyptic number.

1638543694 is a deficient number, since it is larger than the sum of its proper divisors (819271850).

1638543694 is an equidigital number, since it uses as much as digits as its factorization.

1638543694 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 819271849.

The product of its digits is 1866240, while the sum is 49.

The square root of 1638543694 is about 40478.9290125122. The cubic root of 1638543694 is about 1178.9245429599.

The spelling of 1638543694 in words is "one billion, six hundred thirty-eight million, five hundred forty-three thousand, six hundred ninety-four".