21605617711 has 4 divisors (see below), whose sum is σ = 21748701424. Its totient is φ = 21462534000.

The previous prime is 21605617703. The next prime is 21605617721. The reversal of 21605617711 is 11771650612.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21605617711 - 2³ = 21605617703 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21605617721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 71541630 + ... + 71541931.

It is an arithmetic number, because the mean of its divisors is an integer number (5437175356).

Almost surely, 2^21605617711 is an apocalyptic number.

21605617711 is a deficient number, since it is larger than the sum of its proper divisors (143083713).

21605617711 is a wasteful number, since it uses less digits than its factorization.

21605617711 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 143083712.

The product of its (nonzero) digits is 17640, while the sum is 37.

The spelling of 21605617711 in words is "twenty-one billion, six hundred five million, six hundred seventeen thousand, seven hundred eleven".