21101287 has 2 divisors, whose sum is σ = 21101288. Its totient is φ = 21101286.

The previous prime is 21101273. The next prime is 21101293. The reversal of 21101287 is 78210112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21101287 - 2¹⁵ = 21068519 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21101207) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10550643 + 10550644.

It is an arithmetic number, because the mean of its divisors is an integer number (10550644).

Almost surely, 2^21101287 is an apocalyptic number.

21101287 is a deficient number, since it is larger than the sum of its proper divisors (1).

21101287 is an equidigital number, since it uses as much as digits as its factorization.

21101287 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 224, while the sum is 22.

The square root of 21101287 is about 4593.6137190669. The cubic root of 21101287 is about 276.3352669776.

Adding to 21101287 its reverse (78210112), we get a palindrome (99311399).

The spelling of 21101287 in words is "twenty-one million, one hundred one thousand, two hundred eighty-seven".