406740821 has 2 divisors, whose sum is σ = 406740822. Its totient is φ = 406740820.

The previous prime is 406740797. The next prime is 406740823. The reversal of 406740821 is 128047604.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 382632721 + 24108100 = 19561^2 + 4910^2 .

It is a cyclic number.

It is not a de Polignac number, because 406740821 - 2²² = 402546517 is a prime.

Together with 406740823, it forms a pair of twin primes.

It is a Chen prime.

It is equal to p_21676361 and since 406740821 and 21676361 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (406740823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 203370410 + 203370411.

It is an arithmetic number, because the mean of its divisors is an integer number (203370411).

Almost surely, 2^406740821 is an apocalyptic number.

It is an amenable number.

406740821 is a deficient number, since it is larger than the sum of its proper divisors (1).

406740821 is an equidigital number, since it uses as much as digits as its factorization.

406740821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10752, while the sum is 32.

The square root of 406740821 is about 20167.8164658448. The cubic root of 406740821 is about 740.9221648129.

The spelling of 406740821 in words is "four hundred six million, seven hundred forty thousand, eight hundred twenty-one".