1287638778 has 16 divisors (see below), whose sum is σ = 2710818720. Its totient is φ = 406622736.

The previous prime is 1287638777. The next prime is 1287638783. The reversal of 1287638778 is 8778367821.

It is a Harshad number since it is a multiple of its sum of digits (57).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1287638777) 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, 5647425 + ... + 5647652.

It is an arithmetic number, because the mean of its divisors is an integer number (169426170).

Almost surely, 2^1287638778 is an apocalyptic number.

1287638778 is an abundant number, since it is smaller than the sum of its proper divisors (1423179942).

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

1287638778 is a wasteful number, since it uses less digits than its factorization.

1287638778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11295101.

The product of its digits is 6322176, while the sum is 57.

The square root of 1287638778 is about 35883.6840081951. The cubic root of 1287638778 is about 1087.9226427528.

The spelling of 1287638778 in words is "one billion, two hundred eighty-seven million, six hundred thirty-eight thousand, seven hundred seventy-eight".