400001621 has 2 divisors, whose sum is σ = 400001622. Its totient is φ = 400001620.

The previous prime is 400001603. The next prime is 400001639. The reversal of 400001621 is 126100004.

It is a balanced prime because it is at equal distance from previous prime (400001603) and next prime (400001639).

It can be written as a sum of positive squares in only one way, i.e., 207763396 + 192238225 = 14414^2 + 13865^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-400001621 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 400001596 and 400001605.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (400001521) 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, 200000810 + 200000811.

It is an arithmetic number, because the mean of its divisors is an integer number (200000811).

Almost surely, 2^400001621 is an apocalyptic number.

It is an amenable number.

400001621 is a deficient number, since it is larger than the sum of its proper divisors (1).

400001621 is an equidigital number, since it uses as much as digits as its factorization.

400001621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 400001621 is about 20000.0405249589. The cubic root of 400001621 is about 736.8072950292.

Adding to 400001621 its reverse (126100004), we get a palindrome (526101625).

The spelling of 400001621 in words is "four hundred million, one thousand, six hundred twenty-one".