21666013026 has 64 divisors (see below), whose sum is σ = 51186401280. Its totient is φ = 5982799680.

The previous prime is 21666012961. The next prime is 21666013037. The reversal of 21666013026 is 62031066612.

It is a super-2 number, since 2×21666013026² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 1027255 + ... + 1048133.

It is an arithmetic number, because the mean of its divisors is an integer number (799787520).

Almost surely, 2^21666013026 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21666013026, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25593200640).

21666013026 is an abundant number, since it is smaller than the sum of its proper divisors (29520388254).

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

21666013026 is a wasteful number, since it uses less digits than its factorization.

21666013026 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21719.

The product of its (nonzero) digits is 15552, while the sum is 33.

Adding to 21666013026 its reverse (62031066612), we get a palindrome (83697079638).

The spelling of 21666013026 in words is "twenty-one billion, six hundred sixty-six million, thirteen thousand, twenty-six".