21720066552217 has 16 divisors (see below), whose sum is σ = 23829088939200. Its totient is φ = 19633475415040.

The previous prime is 21720066552199. The next prime is 21720066552227. The reversal of 21720066552217 is 71225566002712.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21720066552217 is a prime.

It is a super-2 number, since 2×21720066552217² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21720066552227) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22141773 + ... + 23101909.

It is an arithmetic number, because the mean of its divisors is an integer number (1489318058700).

Almost surely, 2^{21720066552217} is an apocalyptic number.

It is an amenable number.

21720066552217 is a deficient number, since it is larger than the sum of its proper divisors (2109022386983).

21720066552217 is a wasteful number, since it uses less digits than its factorization.

21720066552217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 971816.

The product of its (nonzero) digits is 705600, while the sum is 46.

The spelling of 21720066552217 in words is "twenty-one trillion, seven hundred twenty billion, sixty-six million, five hundred fifty-two thousand, two hundred seventeen".