21201120121261 has 2 divisors, whose sum is σ = 21201120121262. Its totient is φ = 21201120121260.

The previous prime is 21201120121253. The next prime is 21201120121267. The reversal of 21201120121261 is 16212102110212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18180041605636 + 3021078515625 = 4263806^2 + 1738125^2 .

It is a cyclic number.

It is not a de Polignac number, because 21201120121261 - 2³ = 21201120121253 is a prime.

It is a super-2 number, since 2×21201120121261² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21201120121267) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10600560060630 + 10600560060631.

It is an arithmetic number, because the mean of its divisors is an integer number (10600560060631).

Almost surely, 2^{21201120121261} is an apocalyptic number.

It is an amenable number.

21201120121261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21201120121261 is an equidigital number, since it uses as much as digits as its factorization.

21201120121261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 192, while the sum is 22.

Adding to 21201120121261 its reverse (16212102110212), we get a palindrome (37413222231473).

The spelling of 21201120121261 in words is "twenty-one trillion, two hundred one billion, one hundred twenty million, one hundred twenty-one thousand, two hundred sixty-one".