21605011266 has 16 divisors (see below), whose sum is σ = 44025306624. Its totient is φ = 7065789744.

The previous prime is 21605011249. The next prime is 21605011271. The reversal of 21605011266 is 66211050612.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 33969826 + ... + 33970461.

It is an arithmetic number, because the mean of its divisors is an integer number (2751581664).

Almost surely, 2^21605011266 is an apocalyptic number.

21605011266 is an abundant number, since it is smaller than the sum of its proper divisors (22420295358).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21605011266 is a wasteful number, since it uses less digits than its factorization.

21605011266 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67940345.

The product of its (nonzero) digits is 4320, while the sum is 30.

Adding to 21605011266 its reverse (66211050612), we get a palindrome (87816061878).

The spelling of 21605011266 in words is "twenty-one billion, six hundred five million, eleven thousand, two hundred sixty-six".