21605711 has 2 divisors, whose sum is σ = 21605712. Its totient is φ = 21605710.

The previous prime is 21605693. The next prime is 21605747. The reversal of 21605711 is 11750612.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21605711 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21605411) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10802855 + 10802856.

It is an arithmetic number, because the mean of its divisors is an integer number (10802856).

Almost surely, 2^21605711 is an apocalyptic number.

21605711 is a deficient number, since it is larger than the sum of its proper divisors (1).

21605711 is an equidigital number, since it uses as much as digits as its factorization.

21605711 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 420, while the sum is 23.

The square root of 21605711 is about 4648.1943806171. The cubic root of 21605711 is about 278.5198724037.

The spelling of 21605711 in words is "twenty-one million, six hundred five thousand, seven hundred eleven".