21221021021 has 2 divisors, whose sum is σ = 21221021022. Its totient is φ = 21221021020.

The previous prime is 21221021011. The next prime is 21221021113. The reversal of 21221021021 is 12012012212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20388698521 + 832322500 = 142789^2 + 28850^2 .

It is a cyclic number.

It is not a de Polignac number, because 21221021021 - 2²² = 21216826717 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21221020987 and 21221021005.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21221021011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610510510 + 10610510511.

It is an arithmetic number, because the mean of its divisors is an integer number (10610510511).

Almost surely, 2^21221021021 is an apocalyptic number.

It is an amenable number.

21221021021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21221021021 is an equidigital number, since it uses as much as digits as its factorization.

21221021021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32, while the sum is 14.

Adding to 21221021021 its reverse (12012012212), we get a palindrome (33233033233).

The spelling of 21221021021 in words is "twenty-one billion, two hundred twenty-one million, twenty-one thousand, twenty-one".