1638440920 has 16 divisors (see below), whose sum is σ = 3686492160. Its totient is φ = 655376352.

The previous prime is 1638440899. The next prime is 1638440933. The reversal of 1638440920 is 290448361.

It is a self number, because there is not a number n which added to its sum of digits gives 1638440920.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20480472 + ... + 20480551.

It is an arithmetic number, because the mean of its divisors is an integer number (230405760).

Almost surely, 2^1638440920 is an apocalyptic number.

1638440920 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1638440920 is an abundant number, since it is smaller than the sum of its proper divisors (2048051240).

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

1638440920 is a wasteful number, since it uses less digits than its factorization.

1638440920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40961034 (or 40961030 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 37.

The square root of 1638440920 is about 40477.6595173189. The cubic root of 1638440920 is about 1178.8998939734.

The spelling of 1638440920 in words is "one billion, six hundred thirty-eight million, four hundred forty thousand, nine hundred twenty".