1280921 has 2 divisors, whose sum is σ = 1280922. Its totient is φ = 1280920.

The previous prime is 1280887. The next prime is 1280947. The reversal of 1280921 is 1290821.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 697225 + 583696 = 835^2 + 764^2 .

It is a cyclic number.

It is not a de Polignac number, because 1280921 - 2⁶ = 1280857 is a prime.

It is not a weakly prime, because it can be changed into another prime (1280221) 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 as a sum of consecutive naturals, namely, 640460 + 640461.

It is an arithmetic number, because the mean of its divisors is an integer number (640461).

2^1280921 is an apocalyptic number.

It is an amenable number.

1280921 is a deficient number, since it is larger than the sum of its proper divisors (1).

1280921 is an equidigital number, since it uses as much as digits as its factorization.

1280921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 288, while the sum is 23.

The square root of 1280921 is about 1131.7778050483. Note that the first 3 decimals coincide. The cubic root of 1280921 is about 108.6027398644.

It can be divided in two parts, 1280 and 921, that multiplied together give a triangular number (1178880 = T₁₅₃₅).

The spelling of 1280921 in words is "one million, two hundred eighty thousand, nine hundred twenty-one".