1638897990 has 32 divisors (see below), whose sum is σ = 4017047040. Its totient is φ = 427740384.

The previous prime is 1638897941. The next prime is 1638898033. The reversal of 1638897990 is 997988361.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 579760 + ... + 582579.

It is an arithmetic number, because the mean of its divisors is an integer number (125532720).

Almost surely, 2^1638897990 is an apocalyptic number.

1638897990 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

1638897990 is an abundant number, since it is smaller than the sum of its proper divisors (2378149050).

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

1638897990 is a wasteful number, since it uses less digits than its factorization.

1638897990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1162396.

The product of its (nonzero) digits is 5878656, while the sum is 60.

The square root of 1638897990 is about 40483.3050775255. The cubic root of 1638897990 is about 1179.0095082759.

The spelling of 1638897990 in words is "one billion, six hundred thirty-eight million, eight hundred ninety-seven thousand, nine hundred ninety".