11817721 has 2 divisors, whose sum is σ = 11817722. Its totient is φ = 11817720.

The previous prime is 11817709. The next prime is 11817739. The reversal of 11817721 is 12771811.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11799225 + 18496 = 3435^2 + 136^2 .

It is a cyclic number.

It is not a de Polignac number, because 11817721 - 2⁷ = 11817593 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 11817721.

It is not a weakly prime, because it can be changed into another prime (11817121) 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, 5908860 + 5908861.

It is an arithmetic number, because the mean of its divisors is an integer number (5908861).

Almost surely, 2^11817721 is an apocalyptic number.

It is an amenable number.

11817721 is a deficient number, since it is larger than the sum of its proper divisors (1).

11817721 is an equidigital number, since it uses as much as digits as its factorization.

11817721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 784, while the sum is 28.

The square root of 11817721 is about 3437.6912310445. The cubic root of 11817721 is about 227.7777214533. Note that the first 4 decimals are identical.

The spelling of 11817721 in words is "eleven million, eight hundred seventeen thousand, seven hundred twenty-one".