81212981 has 2 divisors, whose sum is σ = 81212982. Its totient is φ = 81212980.

The previous prime is 81212951. The next prime is 81212993. The reversal of 81212981 is 18921218.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 71132356 + 10080625 = 8434^2 + 3175^2 .

It is a cyclic number.

It is not a de Polignac number, because 81212981 - 2¹⁰ = 81211957 is a prime.

It is a super-2 number, since 2×81212981² = 13191096565812722, which contains 22 as substring.

It is a Chen prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81212951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40606490 + 40606491.

It is an arithmetic number, because the mean of its divisors is an integer number (40606491).

Almost surely, 2^81212981 is an apocalyptic number.

It is an amenable number.

81212981 is a deficient number, since it is larger than the sum of its proper divisors (1).

81212981 is an equidigital number, since it uses as much as digits as its factorization.

81212981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2304, while the sum is 32.

The square root of 81212981 is about 9011.8245100534. The cubic root of 81212981 is about 433.0537635898.

The spelling of 81212981 in words is "eighty-one million, two hundred twelve thousand, nine hundred eighty-one".