81286421 has 2 divisors, whose sum is σ = 81286422. Its totient is φ = 81286420.

The previous prime is 81286411. The next prime is 81286441. The reversal of 81286421 is 12468218.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81252196 + 34225 = 9014^2 + 185^2 .

It is a cyclic number.

It is not a de Polignac number, because 81286421 - 2⁶ = 81286357 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81286411) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40643210 + 40643211.

It is an arithmetic number, because the mean of its divisors is an integer number (40643211).

Almost surely, 2^81286421 is an apocalyptic number.

It is an amenable number.

81286421 is a deficient number, since it is larger than the sum of its proper divisors (1).

81286421 is an equidigital number, since it uses as much as digits as its factorization.

81286421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6144, while the sum is 32.

The square root of 81286421 is about 9015.8982358942. The cubic root of 81286421 is about 433.1842595044.

The spelling of 81286421 in words is "eighty-one million, two hundred eighty-six thousand, four hundred twenty-one".