21723333521 has 2 divisors, whose sum is σ = 21723333522. Its totient is φ = 21723333520.

The previous prime is 21723333509. The next prime is 21723333547. The reversal of 21723333521 is 12533332712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21703182400 + 20151121 = 147320^2 + 4489^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21723333521 is a prime.

It is not a weakly prime, because it can be changed into another prime (21723333571) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10861666760 + 10861666761.

It is an arithmetic number, because the mean of its divisors is an integer number (10861666761).

Almost surely, 2^21723333521 is an apocalyptic number.

It is an amenable number.

21723333521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21723333521 is an equidigital number, since it uses as much as digits as its factorization.

21723333521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 22680, while the sum is 32.

The spelling of 21723333521 in words is "twenty-one billion, seven hundred twenty-three million, three hundred thirty-three thousand, five hundred twenty-one".