20721834005689 has 2 divisors, whose sum is σ = 20721834005690. Its totient is φ = 20721834005688.

The previous prime is 20721834005687. The next prime is 20721834005753. The reversal of 20721834005689 is 98650043812702.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14654479765689 + 6067354240000 = 3828117^2 + 2463200^2 .

It is a cyclic number.

It is not a de Polignac number, because 20721834005689 - 2¹ = 20721834005687 is a prime.

Together with 20721834005687, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (20721834005687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10360917002844 + 10360917002845.

It is an arithmetic number, because the mean of its divisors is an integer number (10360917002845).

It is a 1-persistent number, because it is pandigital, but 2⋅20721834005689 = 41443668011378 is not.

Almost surely, 2^{20721834005689} is an apocalyptic number.

It is an amenable number.

20721834005689 is a deficient number, since it is larger than the sum of its proper divisors (1).

20721834005689 is an equidigital number, since it uses as much as digits as its factorization.

20721834005689 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5806080, while the sum is 55.

The spelling of 20721834005689 in words is "twenty trillion, seven hundred twenty-one billion, eight hundred thirty-four million, five thousand, six hundred eighty-nine".