80640821 has 2 divisors, whose sum is σ = 80640822. Its totient is φ = 80640820.

The previous prime is 80640817. The next prime is 80640823. The reversal of 80640821 is 12804608.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 61622500 + 19018321 = 7850^2 + 4361^2 .

It is a cyclic number.

It is not a de Polignac number, because 80640821 - 2² = 80640817 is a prime.

It is a Sophie Germain prime.

Together with 80640823, it forms a pair of twin primes.

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 (80640823) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40320410 + 40320411.

It is an arithmetic number, because the mean of its divisors is an integer number (40320411).

Almost surely, 2^80640821 is an apocalyptic number.

It is an amenable number.

80640821 is a deficient number, since it is larger than the sum of its proper divisors (1).

80640821 is an equidigital number, since it uses as much as digits as its factorization.

80640821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3072, while the sum is 29.

The square root of 80640821 is about 8980.0234409494. The cubic root of 80640821 is about 432.0343854803.

The spelling of 80640821 in words is "eighty million, six hundred forty thousand, eight hundred twenty-one".