9810851621981 has 2 divisors, whose sum is σ = 9810851621982. Its totient is φ = 9810851621980.

The previous prime is 9810851621969. The next prime is 9810851621983. The reversal of 9810851621981 is 1891261580189.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7225026819481 + 2585824802500 = 2687941^2 + 1608050^2 .

It is a cyclic number.

It is not a de Polignac number, because 9810851621981 - 2⁶ = 9810851621917 is a prime.

It is a super-2 number, since 2×9810851621981² (a number of 27 digits) contains 22 as substring.

Together with 9810851621983, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 9810851621981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9810851621983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4905425810990 + 4905425810991.

It is an arithmetic number, because the mean of its divisors is an integer number (4905425810991).

Almost surely, 2^{9810851621981} is an apocalyptic number.

It is an amenable number.

9810851621981 is a deficient number, since it is larger than the sum of its proper divisors (1).

9810851621981 is an equidigital number, since it uses as much as digits as its factorization.

9810851621981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2488320, while the sum is 59.

The spelling of 9810851621981 in words is "nine trillion, eight hundred ten billion, eight hundred fifty-one million, six hundred twenty-one thousand, nine hundred eighty-one".