1247836721 has 2 divisors, whose sum is σ = 1247836722. Its totient is φ = 1247836720.

The previous prime is 1247836697. The next prime is 1247836753. The reversal of 1247836721 is 1276387421.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1232782321 + 15054400 = 35111^2 + 3880^2 .

It is a cyclic number.

It is not a de Polignac number, because 1247836721 - 2²⁶ = 1180727857 is a prime.

It is not a weakly prime, because it can be changed into another prime (1247839721) 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, 623918360 + 623918361.

It is an arithmetic number, because the mean of its divisors is an integer number (623918361).

Almost surely, 2^1247836721 is an apocalyptic number.

It is an amenable number.

1247836721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1247836721 is an equidigital number, since it uses as much as digits as its factorization.

1247836721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 112896, while the sum is 41.

The square root of 1247836721 is about 35324.7324264459. The cubic root of 1247836721 is about 1076.5955670805.

The spelling of 1247836721 in words is "one billion, two hundred forty-seven million, eight hundred thirty-six thousand, seven hundred twenty-one".