1621004321 has 2 divisors, whose sum is σ = 1621004322. Its totient is φ = 1621004320.

The previous prime is 1621004309. The next prime is 1621004351. The reversal of 1621004321 is 1234001261.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1605124096 + 15880225 = 40064^2 + 3985^2 .

It is a cyclic number.

It is not a de Polignac number, because 1621004321 - 2⁶ = 1621004257 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 1621004293 and 1621004302.

It is not a weakly prime, because it can be changed into another prime (1621004351) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 810502160 + 810502161.

It is an arithmetic number, because the mean of its divisors is an integer number (810502161).

Almost surely, 2^1621004321 is an apocalyptic number.

It is an amenable number.

1621004321 is a deficient number, since it is larger than the sum of its proper divisors (1).

1621004321 is an equidigital number, since it uses as much as digits as its factorization.

1621004321 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 1621004321 is about 40261.6979398535. The cubic root of 1621004321 is about 1174.7029449160.

Adding to 1621004321 its reverse (1234001261), we get a palindrome (2855005582).

The spelling of 1621004321 in words is "one billion, six hundred twenty-one million, four thousand, three hundred twenty-one".