21666878870472 has 288 divisors, whose sum is σ = 66376115245440. Its totient is φ = 6376955270400.

The previous prime is 21666878870467. The next prime is 21666878870479. The reversal of 21666878870472 is 27407887866612.

It is a Harshad number since it is a multiple of its sum of digits (72).

It is a self number, because there is not a number n which added to its sum of digits gives 21666878870472.

It is not an unprimeable number, because it can be changed into a prime (21666878870479) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 53437818 + ... + 53841750.

It is an arithmetic number, because the mean of its divisors is an integer number (230472622380).

Almost surely, 2^{21666878870472} is an apocalyptic number.

21666878870472 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 21666878870472, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33188057622720).

21666878870472 is an abundant number, since it is smaller than the sum of its proper divisors (44709236374968).

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

21666878870472 is a wasteful number, since it uses less digits than its factorization.

21666878870472 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 404145 (or 404127 counting only the distinct ones).

The product of its (nonzero) digits is 606928896, while the sum is 72.

The spelling of 21666878870472 in words is "twenty-one trillion, six hundred sixty-six billion, eight hundred seventy-eight million, eight hundred seventy thousand, four hundred seventy-two".