21205567215672 has 128 divisors (see below), whose sum is σ = 60901609190400. Its totient is φ = 6027312872448.

The previous prime is 21205567215671. The next prime is 21205567215737. The reversal of 21205567215672 is 27651276550212.

It is a happy number.

It is a super-3 number, since 3×21205567215672³ (a number of 41 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21205567215671) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 352872604 + ... + 352932692.

It is an arithmetic number, because the mean of its divisors is an integer number (475793821800).

Almost surely, 2^{21205567215672} is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21205567215672, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30450804595200).

21205567215672 is an abundant number, since it is smaller than the sum of its proper divisors (39696041974728).

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

21205567215672 is a wasteful number, since it uses less digits than its factorization.

21205567215672 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70965 (or 70961 counting only the distinct ones).

The product of its (nonzero) digits is 3528000, while the sum is 51.

The spelling of 21205567215672 in words is "twenty-one trillion, two hundred five billion, five hundred sixty-seven million, two hundred fifteen thousand, six hundred seventy-two".