21266155216121 has 2 divisors, whose sum is σ = 21266155216122. Its totient is φ = 21266155216120.

The previous prime is 21266155216079. The next prime is 21266155216147. The reversal of 21266155216121 is 12161255166212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12095336287225 + 9170818928896 = 3477835^2 + 3028336^2 .

It is a cyclic number.

It is not a de Polignac number, because 21266155216121 - 2¹⁸ = 21266154953977 is a prime.

It is not a weakly prime, because it can be changed into another prime (21266155216181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10633077608060 + 10633077608061.

It is an arithmetic number, because the mean of its divisors is an integer number (10633077608061).

Almost surely, 2^{21266155216121} is an apocalyptic number.

It is an amenable number.

21266155216121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21266155216121 is an equidigital number, since it uses as much as digits as its factorization.

21266155216121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 86400, while the sum is 41.

The spelling of 21266155216121 in words is "twenty-one trillion, two hundred sixty-six billion, one hundred fifty-five million, two hundred sixteen thousand, one hundred twenty-one".