1281820 has 12 divisors (see below), whose sum is σ = 2691864. Its totient is φ = 512720.

The previous prime is 1281809. The next prime is 1281821. The reversal of 1281820 is 281821.

1281820 = T₈₂ + T₈₃ + ... + T₂₀₁.

It is a junction number, because it is equal to n+sod(n) for n = 1281791 and 1281800.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1281821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 32026 + ... + 32065.

It is an arithmetic number, because the mean of its divisors is an integer number (224322).

2^1281820 is an apocalyptic number.

1281820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1281820 is an abundant number, since it is smaller than the sum of its proper divisors (1410044).

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

1281820 is a wasteful number, since it uses less digits than its factorization.

1281820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64100 (or 64098 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 22.

The square root of 1281820 is about 1132.1748981496. The cubic root of 1281820 is about 108.6281411267.

Subtracting from 1281820 its reverse (281821), we obtain a palindrome (999999).

The spelling of 1281820 in words is "one million, two hundred eighty-one thousand, eight hundred twenty".