1638420640 has 96 divisors (see below), whose sum is σ = 4052353536. Its totient is φ = 624814080.

The previous prime is 1638420629. The next prime is 1638420659. The reversal of 1638420640 is 460248361.

It is a junction number, because it is equal to n+sod(n) for n = 1638420596 and 1638420605.

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, 1585564 + ... + 1586596.

It is an arithmetic number, because the mean of its divisors is an integer number (42212016).

Almost surely, 2^1638420640 is an apocalyptic number.

1638420640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1638420640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2026176768).

1638420640 is an abundant number, since it is smaller than the sum of its proper divisors (2413932896).

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

1638420640 is a wasteful number, since it uses less digits than its factorization.

1638420640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1502 (or 1494 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 34.

The square root of 1638420640 is about 40477.4090079886. The cubic root of 1638420640 is about 1178.8950299615.

The spelling of 1638420640 in words is "one billion, six hundred thirty-eight million, four hundred twenty thousand, six hundred forty".