81294821 has 2 divisors, whose sum is σ = 81294822. Its totient is φ = 81294820.

The previous prime is 81294779. The next prime is 81294823. The reversal of 81294821 is 12849218.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 80820100 + 474721 = 8990^2 + 689^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81294821 is a prime.

Together with 81294823, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81294823) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40647410 + 40647411.

It is an arithmetic number, because the mean of its divisors is an integer number (40647411).

Almost surely, 2^81294821 is an apocalyptic number.

It is an amenable number.

81294821 is a deficient number, since it is larger than the sum of its proper divisors (1).

81294821 is an equidigital number, since it uses as much as digits as its factorization.

81294821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9216, while the sum is 35.

The square root of 81294821 is about 9016.3640676273. The cubic root of 81294821 is about 433.1991804978.

The spelling of 81294821 in words is "eighty-one million, two hundred ninety-four thousand, eight hundred twenty-one".