21133154981 has 2 divisors, whose sum is σ = 21133154982. Its totient is φ = 21133154980.

The previous prime is 21133154879. The next prime is 21133154983. The reversal of 21133154981 is 18945133112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20957194756 + 175960225 = 144766^2 + 13265^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21133154981 is a prime.

It is a super-2 number, since 2×21133154981² (a number of 21 digits) contains 22 as substring.

Together with 21133154983, 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 (21133154983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10566577490 + 10566577491.

It is an arithmetic number, because the mean of its divisors is an integer number (10566577491).

Almost surely, 2^21133154981 is an apocalyptic number.

It is an amenable number.

21133154981 is a deficient number, since it is larger than the sum of its proper divisors (1).

21133154981 is an equidigital number, since it uses as much as digits as its factorization.

21133154981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25920, while the sum is 38.

The spelling of 21133154981 in words is "twenty-one billion, one hundred thirty-three million, one hundred fifty-four thousand, nine hundred eighty-one".