400221821 has 4 divisors (see below), whose sum is σ = 405288000. Its totient is φ = 395155644.

The previous prime is 400221751. The next prime is 400221889. The reversal of 400221821 is 128122004.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-400221821 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 400221793 and 400221802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (400221221) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2532971 + ... + 2533128.

It is an arithmetic number, because the mean of its divisors is an integer number (101322000).

Almost surely, 2^400221821 is an apocalyptic number.

It is an amenable number.

400221821 is a deficient number, since it is larger than the sum of its proper divisors (5066179).

400221821 is an equidigital number, since it uses as much as digits as its factorization.

400221821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5066178.

The product of its (nonzero) digits is 256, while the sum is 20.

The square root of 400221821 is about 20005.5447563919. The cubic root of 400221821 is about 736.9424738178.

Adding to 400221821 its reverse (128122004), we get a palindrome (528343825).

The spelling of 400221821 in words is "four hundred million, two hundred twenty-one thousand, eight hundred twenty-one".