4891212121981 has 2 divisors, whose sum is σ = 4891212121982. Its totient is φ = 4891212121980.

The previous prime is 4891212121973. The next prime is 4891212122011. The reversal of 4891212121981 is 1891212121984.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 3259346393956 + 1631865728025 = 1805366^2 + 1277445^2 .

It is a cyclic number.

It is not a de Polignac number, because 4891212121981 - 2³ = 4891212121973 is a prime.

It is a super-2 number, since 2×4891212121981² (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 (4891212101981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2445606060990 + 2445606060991.

It is an arithmetic number, because the mean of its divisors is an integer number (2445606060991).

Almost surely, 2^{4891212121981} is an apocalyptic number.

It is an amenable number.

4891212121981 is a deficient number, since it is larger than the sum of its proper divisors (1).

4891212121981 is an equidigital number, since it uses as much as digits as its factorization.

4891212121981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 165888, while the sum is 49.

The spelling of 4891212121981 in words is "four trillion, eight hundred ninety-one billion, two hundred twelve million, one hundred twenty-one thousand, nine hundred eighty-one".