21201211010981 has 2 divisors, whose sum is σ = 21201211010982. Its totient is φ = 21201211010980.

The previous prime is 21201211010951. The next prime is 21201211010983. The reversal of 21201211010981 is 18901011210212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12794864614081 + 8406346396900 = 3576991^2 + 2899370^2 .

It is a cyclic number.

It is not a de Polignac number, because 21201211010981 - 2²⁶ = 21201143902117 is a prime.

It is a super-2 number, since 2×21201211010981² (a number of 27 digits) contains 22 as substring.

Together with 21201211010983, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21201211010983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10600605505490 + 10600605505491.

It is an arithmetic number, because the mean of its divisors is an integer number (10600605505491).

Almost surely, 2^{21201211010981} is an apocalyptic number.

It is an amenable number.

21201211010981 is a deficient number, since it is larger than the sum of its proper divisors (1).

21201211010981 is an equidigital number, since it uses as much as digits as its factorization.

21201211010981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 576, while the sum is 29.

The spelling of 21201211010981 in words is "twenty-one trillion, two hundred one billion, two hundred eleven million, ten thousand, nine hundred eighty-one".