1281391820 has 24 divisors (see below), whose sum is σ = 2777728128. Its totient is φ = 496022400.

The previous prime is 1281391781. The next prime is 1281391823. The reversal of 1281391820 is 281931821.

It is not an unprimeable number, because it can be changed into a prime (1281391823) 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, 1032761 + ... + 1034000.

It is an arithmetic number, because the mean of its divisors is an integer number (115738672).

Almost surely, 2^1281391820 is an apocalyptic number.

1281391820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1281391820 is an abundant number, since it is smaller than the sum of its proper divisors (1496336308).

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

1281391820 is a wasteful number, since it uses less digits than its factorization.

1281391820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2066801 (or 2066799 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 35.

The square root of 1281391820 is about 35796.5336310655. The cubic root of 1281391820 is about 1086.1604437435.

The spelling of 1281391820 in words is "one billion, two hundred eighty-one million, three hundred ninety-one thousand, eight hundred twenty".