21703506221 has 2 divisors, whose sum is σ = 21703506222. Its totient is φ = 21703506220.

The previous prime is 21703506137. The next prime is 21703506271. The reversal of 21703506221 is 12260530712.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17288568196 + 4414938025 = 131486^2 + 66445^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21703506221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21703506271) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10851753110 + 10851753111.

It is an arithmetic number, because the mean of its divisors is an integer number (10851753111).

Almost surely, 2^21703506221 is an apocalyptic number.

It is an amenable number.

21703506221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21703506221 is an equidigital number, since it uses as much as digits as its factorization.

21703506221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5040, while the sum is 29.

The spelling of 21703506221 in words is "twenty-one billion, seven hundred three million, five hundred six thousand, two hundred twenty-one".