400211821 has 2 divisors, whose sum is σ = 400211822. Its totient is φ = 400211820.

The previous prime is 400211813. The next prime is 400211849. The reversal of 400211821 is 128112004.

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., 355134025 + 45077796 = 18845^2 + 6714^2 .

It is a cyclic number.

It is not a de Polignac number, because 400211821 - 2³ = 400211813 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (400211221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 200105910 + 200105911.

It is an arithmetic number, because the mean of its divisors is an integer number (200105911).

Almost surely, 2^400211821 is an apocalyptic number.

It is an amenable number.

400211821 is a deficient number, since it is larger than the sum of its proper divisors (1).

400211821 is an equidigital number, since it uses as much as digits as its factorization.

400211821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 128, while the sum is 19.

The square root of 400211821 is about 20005.2948241209. The cubic root of 400211821 is about 736.9363359831.

Adding to 400211821 its reverse (128112004), we get a palindrome (528323825).

The spelling of 400211821 in words is "four hundred million, two hundred eleven thousand, eight hundred twenty-one".