81280421 has 2 divisors, whose sum is σ = 81280422. Its totient is φ = 81280420.

The previous prime is 81280373. The next prime is 81280477. The reversal of 81280421 is 12408218.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 62884900 + 18395521 = 7930^2 + 4289^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81280421 is a prime.

It is a Sophie Germain 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 (81280921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40640210 + 40640211.

It is an arithmetic number, because the mean of its divisors is an integer number (40640211).

Almost surely, 2^81280421 is an apocalyptic number.

It is an amenable number.

81280421 is a deficient number, since it is larger than the sum of its proper divisors (1).

81280421 is an equidigital number, since it uses as much as digits as its factorization.

81280421 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1024, while the sum is 26.

The square root of 81280421 is about 9015.5654842056. The cubic root of 81280421 is about 433.1736010226.

Adding to 81280421 its reverse (12408218), we get a palindrome (93688639).

The spelling of 81280421 in words is "eighty-one million, two hundred eighty thousand, four hundred twenty-one".