400721 has 2 divisors, whose sum is σ = 400722. Its totient is φ = 400720.

The previous prime is 400711. The next prime is 400723. The reversal of 400721 is 127004.

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., 270400 + 130321 = 520^2 + 361^2 .

It is a cyclic number.

It is not a de Polignac number, because 400721 - 2⁶ = 400657 is a prime.

Together with 400723, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 400696 and 400705.

It is not a weakly prime, because it can be changed into another prime (400723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 200360 + 200361.

It is an arithmetic number, because the mean of its divisors is an integer number (200361).

2⁴⁰⁰⁷²¹ is an apocalyptic number.

It is an amenable number.

400721 is a deficient number, since it is larger than the sum of its proper divisors (1).

400721 is an equidigital number, since it uses as much as digits as its factorization.

400721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 56, while the sum is 14.

The square root of 400721 is about 633.0252759567. The cubic root of 400721 is about 73.7248731792.

Adding to 400721 its reverse (127004), we get a palindrome (527725).

The spelling of 400721 in words is "four hundred thousand, seven hundred twenty-one", and thus it is an iban number.