81121996829 has 2 divisors, whose sum is σ = 81121996830. Its totient is φ = 81121996828.

The previous prime is 81121996819. The next prime is 81121996853. The reversal of 81121996829 is 92869912118.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 78304828900 + 2817167929 = 279830^2 + 53077^2 .

It is a cyclic number.

It is not a de Polignac number, because 81121996829 - 2³⁶ = 12402520093 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81121996819) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40560998414 + 40560998415.

It is an arithmetic number, because the mean of its divisors is an integer number (40560998415).

Almost surely, 2^81121996829 is an apocalyptic number.

It is an amenable number.

81121996829 is a deficient number, since it is larger than the sum of its proper divisors (1).

81121996829 is an equidigital number, since it uses as much as digits as its factorization.

81121996829 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1119744, while the sum is 56.

The spelling of 81121996829 in words is "eighty-one billion, one hundred twenty-one million, nine hundred ninety-six thousand, eight hundred twenty-nine".