21716287 has 2 divisors, whose sum is σ = 21716288. Its totient is φ = 21716286.

The previous prime is 21716251. The next prime is 21716291. The reversal of 21716287 is 78261712.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21716287 - 2⁷ = 21716159 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21716237) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10858143 + 10858144.

It is an arithmetic number, because the mean of its divisors is an integer number (10858144).

Almost surely, 2^21716287 is an apocalyptic number.

21716287 is a deficient number, since it is larger than the sum of its proper divisors (1).

21716287 is an equidigital number, since it uses as much as digits as its factorization.

21716287 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9408, while the sum is 34.

The square root of 21716287 is about 4660.0737118634. The cubic root of 21716287 is about 278.9942103002.

Adding to 21716287 its reverse (78261712), we get a palindrome (99977999).

The spelling of 21716287 in words is "twenty-one million, seven hundred sixteen thousand, two hundred eighty-seven".