1280238721 has 2 divisors, whose sum is σ = 1280238722. Its totient is φ = 1280238720.

The previous prime is 1280238709. The next prime is 1280238779. The reversal of 1280238721 is 1278320821.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1122987121 + 157251600 = 33511^2 + 12540^2 .

It is a cyclic number.

It is not a de Polignac number, because 1280238721 - 2¹¹ = 1280236673 is a prime.

It is a super-2 number, since 2×1280238721² = 3278022365495431682, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1280232721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 640119360 + 640119361.

It is an arithmetic number, because the mean of its divisors is an integer number (640119361).

Almost surely, 2^1280238721 is an apocalyptic number.

It is an amenable number.

1280238721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1280238721 is an equidigital number, since it uses as much as digits as its factorization.

1280238721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10752, while the sum is 34.

The square root of 1280238721 is about 35780.4237118567. The cubic root of 1280238721 is about 1085.8345412430.

The spelling of 1280238721 in words is "one billion, two hundred eighty million, two hundred thirty-eight thousand, seven hundred twenty-one".