21121122221081 has 2 divisors, whose sum is σ = 21121122221082. Its totient is φ = 21121122221080.

The previous prime is 21121122221039. The next prime is 21121122221167. The reversal of 21121122221081 is 18012222112112.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19109277845056 + 2011844376025 = 4371416^2 + 1418395^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21121122221081 is a prime.

It is a super-2 number, since 2×21121122221081² (a number of 27 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21121122221081.

It is not a weakly prime, because it can be changed into another prime (21121122221011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10560561110540 + 10560561110541.

It is an arithmetic number, because the mean of its divisors is an integer number (10560561110541).

Almost surely, 2^{21121122221081} is an apocalyptic number.

It is an amenable number.

21121122221081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21121122221081 is an equidigital number, since it uses as much as digits as its factorization.

21121122221081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 512, while the sum is 26.

Adding to 21121122221081 its reverse (18012222112112), we get a palindrome (39133344333193).

The spelling of 21121122221081 in words is "twenty-one trillion, one hundred twenty-one billion, one hundred twenty-two million, two hundred twenty-one thousand, eighty-one".