21312020161 has 2 divisors, whose sum is σ = 21312020162. Its totient is φ = 21312020160.

The previous prime is 21312020137. The next prime is 21312020207. The reversal of 21312020161 is 16102021312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14568490000 + 6743530161 = 120700^2 + 82119^2 .

It is a cyclic number.

It is not a de Polignac number, because 21312020161 - 2⁷ = 21312020033 is a prime.

It is not a weakly prime, because it can be changed into another prime (21312020101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10656010080 + 10656010081.

It is an arithmetic number, because the mean of its divisors is an integer number (10656010081).

Almost surely, 2^21312020161 is an apocalyptic number.

It is an amenable number.

21312020161 is a deficient number, since it is larger than the sum of its proper divisors (1).

21312020161 is an equidigital number, since it uses as much as digits as its factorization.

21312020161 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 144, while the sum is 19.

Adding to 21312020161 its reverse (16102021312), we get a palindrome (37414041473).

The spelling of 21312020161 in words is "twenty-one billion, three hundred twelve million, twenty thousand, one hundred sixty-one".