11215781 has 2 divisors, whose sum is σ = 11215782. Its totient is φ = 11215780.

The previous prime is 11215759. The next prime is 11215811. The reversal of 11215781 is 18751211.

11215781 is digitally balanced in base 2 and base 3, because in such bases it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6225025 + 4990756 = 2495^2 + 2234^2 .

It is an emirp because it is prime and its reverse (18751211) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 11215781 - 2⁶ = 11215717 is a prime.

It is a super-2 number, since 2×11215781² = 251587486879922, which contains 22 as substring.

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 11215781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (11215741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5607890 + 5607891.

It is an arithmetic number, because the mean of its divisors is an integer number (5607891).

Almost surely, 2^11215781 is an apocalyptic number.

It is an amenable number.

11215781 is a deficient number, since it is larger than the sum of its proper divisors (1).

11215781 is an equidigital number, since it uses as much as digits as its factorization.

11215781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 560, while the sum is 26.

The square root of 11215781 is about 3348.9970140327. The cubic root of 11215781 is about 223.8428226131.

Adding to 11215781 its reverse (18751211), we get a palindrome (29966992).

The spelling of 11215781 in words is "eleven million, two hundred fifteen thousand, seven hundred eighty-one".