21111287 has 2 divisors, whose sum is σ = 21111288. Its totient is φ = 21111286.

The previous prime is 21111283. The next prime is 21111301. The reversal of 21111287 is 78211112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21111287 - 2² = 21111283 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21111283) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10555643 + 10555644.

It is an arithmetic number, because the mean of its divisors is an integer number (10555644).

Almost surely, 2^21111287 is an apocalyptic number.

21111287 is a deficient number, since it is larger than the sum of its proper divisors (1).

21111287 is an equidigital number, since it uses as much as digits as its factorization.

21111287 is an evil number, because the sum of its binary digits is even.

The product of its digits is 224, while the sum is 23.

The square root of 21111287 is about 4594.7020578053. The cubic root of 21111287 is about 276.3789122816.

Adding to 21111287 its reverse (78211112), we get a palindrome (99322399).

The spelling of 21111287 in words is "twenty-one million, one hundred eleven thousand, two hundred eighty-seven".