1638404938 has 8 divisors (see below), whose sum is σ = 2542352580. Its totient is φ = 790954080.

The previous prime is 1638404921. The next prime is 1638404939. The reversal of 1638404938 is 8394048361.

It can be written as a sum of positive squares in 2 ways, for example, as 1610978769 + 27426169 = 40137^2 + 5237^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (1638404939) 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, 14124123 + ... + 14124238.

Almost surely, 2^1638404938 is an apocalyptic number.

1638404938 is a deficient number, since it is larger than the sum of its proper divisors (903947642).

1638404938 is a wasteful number, since it uses less digits than its factorization.

1638404938 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28248392.

The product of its (nonzero) digits is 497664, while the sum is 46.

The square root of 1638404938 is about 40477.2150474807. The cubic root of 1638404938 is about 1178.8912639223.

The spelling of 1638404938 in words is "one billion, six hundred thirty-eight million, four hundred four thousand, nine hundred thirty-eight".