21740287 has 2 divisors, whose sum is σ = 21740288. Its totient is φ = 21740286.

The previous prime is 21740281. The next prime is 21740309. The reversal of 21740287 is 78204712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21740287 - 2¹¹ = 21738239 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 (21740281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10870143 + 10870144.

It is an arithmetic number, because the mean of its divisors is an integer number (10870144).

Almost surely, 2^21740287 is an apocalyptic number.

21740287 is a deficient number, since it is larger than the sum of its proper divisors (1).

21740287 is an equidigital number, since it uses as much as digits as its factorization.

21740287 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6272, while the sum is 31.

The square root of 21740287 is about 4662.6480673540. The cubic root of 21740287 is about 279.0969503296.

Adding to 21740287 its reverse (78204712), we get a palindrome (99944999).

It can be divided in two parts, 217 and 40287, that added together give a palindrome (40504).

The spelling of 21740287 in words is "twenty-one million, seven hundred forty thousand, two hundred eighty-seven".