21720355038523 has 2 divisors, whose sum is σ = 21720355038524. Its totient is φ = 21720355038522.

The previous prime is 21720355038509. The next prime is 21720355038527. The reversal of 21720355038523 is 32583055302712.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21720355038523 is a prime.

It is not a weakly prime, because it can be changed into another prime (21720355038527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10860177519261 + 10860177519262.

It is an arithmetic number, because the mean of its divisors is an integer number (10860177519262).

Almost surely, 2^{21720355038523} is an apocalyptic number.

21720355038523 is a deficient number, since it is larger than the sum of its proper divisors (1).

21720355038523 is an equidigital number, since it uses as much as digits as its factorization.

21720355038523 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1512000, while the sum is 46.

The spelling of 21720355038523 in words is "twenty-one trillion, seven hundred twenty billion, three hundred fifty-five million, thirty-eight thousand, five hundred twenty-three".