21720350563 has 2 divisors, whose sum is σ = 21720350564. Its totient is φ = 21720350562.

The previous prime is 21720350551. The next prime is 21720350573. The reversal of 21720350563 is 36505302712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21720350563 - 2⁹ = 21720350051 is a prime.

It is a super-5 number, since 5×21720350563⁵ (a number of 53 digits) contains 55555 as substring. Note that it is a super-d number also for d = 2.

It is not a weakly prime, because it can be changed into another prime (21720350513) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10860175281 + 10860175282.

It is an arithmetic number, because the mean of its divisors is an integer number (10860175282).

Almost surely, 2^21720350563 is an apocalyptic number.

21720350563 is a deficient number, since it is larger than the sum of its proper divisors (1).

21720350563 is an equidigital number, since it uses as much as digits as its factorization.

21720350563 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 37800, while the sum is 34.

The spelling of 21720350563 in words is "twenty-one billion, seven hundred twenty million, three hundred fifty thousand, five hundred sixty-three".