401021821 has 2 divisors, whose sum is σ = 401021822. Its totient is φ = 401021820.

The previous prime is 401021759. The next prime is 401021833. The reversal of 401021821 is 128120104.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 243016921 + 158004900 = 15589^2 + 12570^2 .

It is a cyclic number.

It is not a de Polignac number, because 401021821 - 2¹⁹ = 400497533 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (401021851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 200510910 + 200510911.

It is an arithmetic number, because the mean of its divisors is an integer number (200510911).

Almost surely, 2^401021821 is an apocalyptic number.

It is an amenable number.

401021821 is a deficient number, since it is larger than the sum of its proper divisors (1).

401021821 is an equidigital number, since it uses as much as digits as its factorization.

401021821 is an evil number, because the sum of its binary digits is even.

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

The square root of 401021821 is about 20025.5292314585. The cubic root of 401021821 is about 737.4331696983.

Adding to 401021821 its reverse (128120104), we get a palindrome (529141925).

The spelling of 401021821 in words is "four hundred one million, twenty-one thousand, eight hundred twenty-one".