1638974640 has 80 divisors (see below), whose sum is σ = 5128386048. Its totient is φ = 432968448.

The previous prime is 1638974621. The next prime is 1638974663. The reversal of 1638974640 is 464798361.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a self number, because there is not a number n which added to its sum of digits gives 1638974640.

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, 6232 + ... + 57591.

Almost surely, 2^1638974640 is an apocalyptic number.

1638974640 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 1638974640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2564193024).

1638974640 is an abundant number, since it is smaller than the sum of its proper divisors (3489411408).

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

1638974640 is a wasteful number, since it uses less digits than its factorization.

1638974640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63946 (or 63940 counting only the distinct ones).

The product of its (nonzero) digits is 870912, while the sum is 48.

The square root of 1638974640 is about 40484.2517529965. The cubic root of 1638974640 is about 1179.0278884457.

The spelling of 1638974640 in words is "one billion, six hundred thirty-eight million, nine hundred seventy-four thousand, six hundred forty".