1638670720 has 64 divisors (see below), whose sum is σ = 3983936400. Its totient is φ = 644343808.

The previous prime is 1638670717. The next prime is 1638670721. The reversal of 1638670720 is 270768361.

It is a tau number, because it is divible by the number of its divisors (64).

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1638670721) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16062 + ... + 59458.

Almost surely, 2^1638670720 is an apocalyptic number.

1638670720 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 1638670720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1991968200).

1638670720 is an abundant number, since it is smaller than the sum of its proper divisors (2345265680).

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

1638670720 is an equidigital number, since it uses as much as digits as its factorization.

1638670720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43475 (or 43463 counting only the distinct ones).

The product of its (nonzero) digits is 84672, while the sum is 40.

The square root of 1638670720 is about 40480.4980206519. The cubic root of 1638670720 is about 1178.9550070441.

The spelling of 1638670720 in words is "one billion, six hundred thirty-eight million, six hundred seventy thousand, seven hundred twenty".