1638651440 has 40 divisors (see below), whose sum is σ = 3862068288. Its totient is φ = 646479360.

The previous prime is 1638651419. The next prime is 1638651451. The reversal of 1638651440 is 441568361.

It is a tau number, because it is divible by the number of its divisors (40).

It is a junction number, because it is equal to n+sod(n) for n = 1638651394 and 1638651403.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 134456 + ... + 146135.

Almost surely, 2^1638651440 is an apocalyptic number.

1638651440 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1638651440 is an abundant number, since it is smaller than the sum of its proper divisors (2223416848).

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

1638651440 is a wasteful number, since it uses less digits than its factorization.

1638651440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 280677 (or 280671 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 38.

The square root of 1638651440 is about 40480.2598805887. The cubic root of 1638651440 is about 1178.9503833083.

The spelling of 1638651440 in words is "one billion, six hundred thirty-eight million, six hundred fifty-one thousand, four hundred forty".