12216781 has 2 divisors, whose sum is σ = 12216782. Its totient is φ = 12216780.

The previous prime is 12216767. The next prime is 12216803. The reversal of 12216781 is 18761221.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10666756 + 1550025 = 3266^2 + 1245^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-12216781 is a prime.

It is a super-2 number, since 2×12216781² = 298499476003922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (12216731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6108390 + 6108391.

It is an arithmetic number, because the mean of its divisors is an integer number (6108391).

Almost surely, 2^12216781 is an apocalyptic number.

It is an amenable number.

12216781 is a deficient number, since it is larger than the sum of its proper divisors (1).

12216781 is an equidigital number, since it uses as much as digits as its factorization.

12216781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1344, while the sum is 28.

The square root of 12216781 is about 3495.2512069950. The cubic root of 12216781 is about 230.3132530643.

The spelling of 12216781 in words is "twelve million, two hundred sixteen thousand, seven hundred eighty-one".