21981104565533 has 2 divisors, whose sum is σ = 21981104565534. Its totient is φ = 21981104565532.

The previous prime is 21981104565503. The next prime is 21981104565547. The reversal of 21981104565533 is 33556540118912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12250966019044 + 9730138546489 = 3500138^2 + 3119317^2 .

It is a cyclic number.

It is not a de Polignac number, because 21981104565533 - 2¹⁶ = 21981104499997 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21981104565503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10990552282766 + 10990552282767.

It is an arithmetic number, because the mean of its divisors is an integer number (10990552282767).

Almost surely, 2^{21981104565533} is an apocalyptic number.

It is an amenable number.

21981104565533 is a deficient number, since it is larger than the sum of its proper divisors (1).

21981104565533 is an equidigital number, since it uses as much as digits as its factorization.

21981104565533 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3888000, while the sum is 53.

The spelling of 21981104565533 in words is "twenty-one trillion, nine hundred eighty-one billion, one hundred four million, five hundred sixty-five thousand, five hundred thirty-three".