21266555566212 has 288 divisors, whose sum is σ = 64192830145920. Its totient is φ = 6063019776000.

The previous prime is 21266555566211. The next prime is 21266555566219.

It is a happy number.

21266555566212 is a `hidden beast` number, since 2 + 1 + 2 + 6 + 6 + 5 + 5 + 5 + 5 + 6 + 621 + 2 = 666.

21266555566212 is nontrivially palindromic in base 10.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is not an unprimeable number, because it can be changed into a prime (21266555566211) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 633349968 + ... + 633383544.

It is an arithmetic number, because the mean of its divisors is an integer number (222891771340).

Almost surely, 2^{21266555566212} is an apocalyptic number.

21266555566212 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21266555566212, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32096415072960).

21266555566212 is an abundant number, since it is smaller than the sum of its proper divisors (42926274579708).

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

21266555566212 is a wasteful number, since it uses less digits than its factorization.

21266555566212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36480 (or 36461 counting only the distinct ones).

The product of its digits is 12960000, while the sum is 54.

The spelling of 21266555566212 in words is "twenty-one trillion, two hundred sixty-six billion, five hundred fifty-five million, five hundred sixty-six thousand, two hundred twelve".