3121821647981 has 2 divisors, whose sum is σ = 3121821647982. Its totient is φ = 3121821647980.

The previous prime is 3121821647953. The next prime is 3121821648037. The reversal of 3121821647981 is 1897461281213.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 2271259984900 + 850561663081 = 1507070^2 + 922259^2 .

It is a cyclic number.

It is not a de Polignac number, because 3121821647981 - 2²⁶ = 3121754539117 is a prime.

It is a super-2 number, since 2×3121821647981² (a number of 26 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (3121821646981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1560910823990 + 1560910823991.

It is an arithmetic number, because the mean of its divisors is an integer number (1560910823991).

Almost surely, 2^{3121821647981} is an apocalyptic number.

It is an amenable number.

3121821647981 is a deficient number, since it is larger than the sum of its proper divisors (1).

3121821647981 is an equidigital number, since it uses as much as digits as its factorization.

3121821647981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1161216, while the sum is 53.

The spelling of 3121821647981 in words is "three trillion, one hundred twenty-one billion, eight hundred twenty-one million, six hundred forty-seven thousand, nine hundred eighty-one".