1638377818 has 24 divisors (see below), whose sum is σ = 3118695264. Its totient is φ = 638328600.

The previous prime is 1638377813. The next prime is 1638377857. The reversal of 1638377818 is 8187738361.

It is a super-2 number, since 2×1638377818² = 5368563749028882248, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (1638377813) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 758838 + ... + 760993.

It is an arithmetic number, because the mean of its divisors is an integer number (129945636).

Almost surely, 2^1638377818 is an apocalyptic number.

1638377818 is a deficient number, since it is larger than the sum of its proper divisors (1480317446).

1638377818 is a wasteful number, since it uses less digits than its factorization.

1638377818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1519858 (or 1519851 counting only the distinct ones).

The product of its digits is 1354752, while the sum is 52.

The square root of 1638377818 is about 40476.8800428096. The cubic root of 1638377818 is about 1178.8847592814.

It can be divided in two parts, 1638 and 377818, that added together give a square (379456 = 616²).

The spelling of 1638377818 in words is "one billion, six hundred thirty-eight million, three hundred seventy-seven thousand, eight hundred eighteen".