1281378840 has 128 divisors (see below), whose sum is σ = 4412828160. Its totient is φ = 291585024.

The previous prime is 1281378823. The next prime is 1281378841. The reversal of 1281378840 is 488731821.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a junction number, because it is equal to n+sod(n) for n = 1281378792 and 1281378801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1281378841) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 192447 + ... + 198993.

It is an arithmetic number, because the mean of its divisors is an integer number (34475220).

Almost surely, 2^1281378840 is an apocalyptic number.

1281378840 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 1281378840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2206414080).

1281378840 is an abundant number, since it is smaller than the sum of its proper divisors (3131449320).

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

1281378840 is a wasteful number, since it uses less digits than its factorization.

1281378840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6801 (or 6797 counting only the distinct ones).

The product of its (nonzero) digits is 86016, while the sum is 42.

The square root of 1281378840 is about 35796.3523281353. The cubic root of 1281378840 is about 1086.1567762703.

The spelling of 1281378840 in words is "one billion, two hundred eighty-one million, three hundred seventy-eight thousand, eight hundred forty".