21021020161 has 2 divisors, whose sum is σ = 21021020162. Its totient is φ = 21021020160.

The previous prime is 21021020159. The next prime is 21021020239. The reversal of 21021020161 is 16102012012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14103937600 + 6917082561 = 118760^2 + 83169^2 .

It is a cyclic number.

It is not a de Polignac number, because 21021020161 - 2¹ = 21021020159 is a prime.

Together with 21021020159, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21021027161) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510510080 + 10510510081.

It is an arithmetic number, because the mean of its divisors is an integer number (10510510081).

Almost surely, 2^21021020161 is an apocalyptic number.

It is an amenable number.

21021020161 is a deficient number, since it is larger than the sum of its proper divisors (1).

21021020161 is an equidigital number, since it uses as much as digits as its factorization.

21021020161 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 48, while the sum is 16.

Adding to 21021020161 its reverse (16102012012), we get a palindrome (37123032173).

The spelling of 21021020161 in words is "twenty-one billion, twenty-one million, twenty thousand, one hundred sixty-one".