21505510573 has 2 divisors, whose sum is σ = 21505510574. Its totient is φ = 21505510572.

The previous prime is 21505510489. The next prime is 21505510613. The reversal of 21505510573 is 37501550512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15594514884 + 5910995689 = 124878^2 + 76883^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21505510573 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21505510973) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10752755286 + 10752755287.

It is an arithmetic number, because the mean of its divisors is an integer number (10752755287).

Almost surely, 2^21505510573 is an apocalyptic number.

It is an amenable number.

21505510573 is a deficient number, since it is larger than the sum of its proper divisors (1).

21505510573 is an equidigital number, since it uses as much as digits as its factorization.

21505510573 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 26250, while the sum is 34.

The spelling of 21505510573 in words is "twenty-one billion, five hundred five million, five hundred ten thousand, five hundred seventy-three".