21688411 has 2 divisors, whose sum is σ = 21688412. Its totient is φ = 21688410.

The previous prime is 21688409. The next prime is 21688421. The reversal of 21688411 is 11488612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21688411 - 2¹ = 21688409 is a prime.

Together with 21688409, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21688421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10844205 + 10844206.

It is an arithmetic number, because the mean of its divisors is an integer number (10844206).

Almost surely, 2^21688411 is an apocalyptic number.

21688411 is a deficient number, since it is larger than the sum of its proper divisors (1).

21688411 is an equidigital number, since it uses as much as digits as its factorization.

21688411 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3072, while the sum is 31.

The square root of 21688411 is about 4657.0818116069. The cubic root of 21688411 is about 278.8747826909.

The spelling of 21688411 in words is "twenty-one million, six hundred eighty-eight thousand, four hundred eleven".