21742087 has 2 divisors, whose sum is σ = 21742088. Its totient is φ = 21742086.

The previous prime is 21742043. The next prime is 21742111. The reversal of 21742087 is 78024712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21742087 - 2⁷ = 21741959 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 (21742027) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10871043 + 10871044.

It is an arithmetic number, because the mean of its divisors is an integer number (10871044).

Almost surely, 2^21742087 is an apocalyptic number.

21742087 is a deficient number, since it is larger than the sum of its proper divisors (1).

21742087 is an equidigital number, since it uses as much as digits as its factorization.

21742087 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21742087 is about 4662.8410867196. The cubic root of 21742087 is about 279.1046527831.

Adding to 21742087 its reverse (78024712), we get a palindrome (99766799).

The spelling of 21742087 in words is "twenty-one million, seven hundred forty-two thousand, eighty-seven".