21704115221 has 2 divisors, whose sum is σ = 21704115222. Its totient is φ = 21704115220.

The previous prime is 21704115211. The next prime is 21704115241. The reversal of 21704115221 is 12251140712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20343316900 + 1360798321 = 142630^2 + 36889^2 .

It is a cyclic number.

It is not a de Polignac number, because 21704115221 - 2¹⁴ = 21704098837 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21704115211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10852057610 + 10852057611.

It is an arithmetic number, because the mean of its divisors is an integer number (10852057611).

Almost surely, 2^21704115221 is an apocalyptic number.

It is an amenable number.

21704115221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21704115221 is an equidigital number, since it uses as much as digits as its factorization.

21704115221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1120, while the sum is 26.

Adding to 21704115221 its reverse (12251140712), we get a palindrome (33955255933).

The spelling of 21704115221 in words is "twenty-one billion, seven hundred four million, one hundred fifteen thousand, two hundred twenty-one".