1638774990 has 48 divisors (see below), whose sum is σ = 4418629488. Its totient is φ = 437006016.

The previous prime is 1638774953. The next prime is 1638775031. The reversal of 1638774990 is 994778361.

It is a happy number.

It is a Smith number, since the sum of its digits (54) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 334767 + ... + 339626.

It is an arithmetic number, because the mean of its divisors is an integer number (92054781).

Almost surely, 2^1638774990 is an apocalyptic number.

1638774990 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

1638774990 is an abundant number, since it is smaller than the sum of its proper divisors (2779854498).

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

1638774990 is an equidigital number, since it uses as much as digits as its factorization.

1638774990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 674415 (or 674403 counting only the distinct ones).

The product of its (nonzero) digits is 2286144, while the sum is 54.

The square root of 1638774990 is about 40481.7859042805. The cubic root of 1638774990 is about 1178.9800124809.

The spelling of 1638774990 in words is "one billion, six hundred thirty-eight million, seven hundred seventy-four thousand, nine hundred ninety".