81420397 has 2 divisors, whose sum is σ = 81420398. Its totient is φ = 81420396.

The previous prime is 81420389. The next prime is 81420407. The reversal of 81420397 is 79302418.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 44769481 + 36650916 = 6691^2 + 6054^2 .

It is a cyclic number.

It is not a de Polignac number, because 81420397 - 2³ = 81420389 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81420337) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40710198 + 40710199.

It is an arithmetic number, because the mean of its divisors is an integer number (40710199).

Almost surely, 2^81420397 is an apocalyptic number.

It is an amenable number.

81420397 is a deficient number, since it is larger than the sum of its proper divisors (1).

81420397 is an equidigital number, since it uses as much as digits as its factorization.

81420397 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12096, while the sum is 34.

The square root of 81420397 is about 9023.3251631535. The cubic root of 81420397 is about 433.4221198084.

The spelling of 81420397 in words is "eighty-one million, four hundred twenty thousand, three hundred ninety-seven".