21361635221 has 2 divisors, whose sum is σ = 21361635222. Its totient is φ = 21361635220.

The previous prime is 21361635179. The next prime is 21361635283. The reversal of 21361635221 is 12253616312.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12624994321 + 8736640900 = 112361^2 + 93470^2 .

It is a cyclic number.

It is not a de Polignac number, because 21361635221 - 2¹⁰ = 21361634197 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21361635121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10680817610 + 10680817611.

It is an arithmetic number, because the mean of its divisors is an integer number (10680817611).

Almost surely, 2^21361635221 is an apocalyptic number.

It is an amenable number.

21361635221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21361635221 is an equidigital number, since it uses as much as digits as its factorization.

21361635221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12960, while the sum is 32.

The spelling of 21361635221 in words is "twenty-one billion, three hundred sixty-one million, six hundred thirty-five thousand, two hundred twenty-one".