21717071 has 2 divisors, whose sum is σ = 21717072. Its totient is φ = 21717070.

The previous prime is 21717067. The next prime is 21717089. The reversal of 21717071 is 17071712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21717071 - 2² = 21717067 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21717071.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21717061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10858535 + 10858536.

It is an arithmetic number, because the mean of its divisors is an integer number (10858536).

Almost surely, 2^21717071 is an apocalyptic number.

21717071 is a deficient number, since it is larger than the sum of its proper divisors (1).

21717071 is an equidigital number, since it uses as much as digits as its factorization.

21717071 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 686, while the sum is 26.

The square root of 21717071 is about 4660.1578299452. The cubic root of 21717071 is about 278.9975676702.

Adding to 21717071 its reverse (17071712), we get a palindrome (38788783).

The spelling of 21717071 in words is "twenty-one million, seven hundred seventeen thousand, seventy-one".