21642302221 has 2 divisors, whose sum is σ = 21642302222. Its totient is φ = 21642302220.

The previous prime is 21642302197. The next prime is 21642302239. The reversal of 21642302221 is 12220324612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11519728900 + 10122573321 = 107330^2 + 100611^2 .

It is a cyclic number.

It is not a de Polignac number, because 21642302221 - 2¹⁹ = 21641777933 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21642302261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10821151110 + 10821151111.

It is an arithmetic number, because the mean of its divisors is an integer number (10821151111).

Almost surely, 2^21642302221 is an apocalyptic number.

It is an amenable number.

21642302221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21642302221 is an equidigital number, since it uses as much as digits as its factorization.

21642302221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2304, while the sum is 25.

Adding to 21642302221 its reverse (12220324612), we get a palindrome (33862626833).

The spelling of 21642302221 in words is "twenty-one billion, six hundred forty-two million, three hundred two thousand, two hundred twenty-one".