1287921840 has 80 divisors (see below), whose sum is σ = 4202707200. Its totient is φ = 325368576.

The previous prime is 1287921839. The next prime is 1287921857. The reversal of 1287921840 is 481297821.

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

It is a junction number, because it is equal to n+sod(n) for n = 1287921792 and 1287921801.

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, 136660 + ... + 145779.

It is an arithmetic number, because the mean of its divisors is an integer number (52533840).

Almost surely, 2^1287921840 is an apocalyptic number.

1287921840 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1287921840 is an abundant number, since it is smaller than the sum of its proper divisors (2914785360).

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

1287921840 is a wasteful number, since it uses less digits than its factorization.

1287921840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 282474 (or 282468 counting only the distinct ones).

The product of its (nonzero) digits is 64512, while the sum is 42.

The square root of 1287921840 is about 35887.6279517050. The cubic root of 1287921840 is about 1088.0023563602.

The spelling of 1287921840 in words is "one billion, two hundred eighty-seven million, nine hundred twenty-one thousand, eight hundred forty".