20404421 has 2 divisors, whose sum is σ = 20404422. Its totient is φ = 20404420.

The previous prime is 20404411. The next prime is 20404441. The reversal of 20404421 is 12440402.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15319396 + 5085025 = 3914^2 + 2255^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20404421 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20404421.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20404411) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10202210 + 10202211.

It is an arithmetic number, because the mean of its divisors is an integer number (10202211).

Almost surely, 2^20404421 is an apocalyptic number.

It is an amenable number.

20404421 is a deficient number, since it is larger than the sum of its proper divisors (1).

20404421 is an equidigital number, since it uses as much as digits as its factorization.

20404421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 256, while the sum is 17.

The square root of 20404421 is about 4517.1253026676. The cubic root of 20404421 is about 273.2591786081.

Adding to 20404421 its reverse (12440402), we get a palindrome (32844823).

The spelling of 20404421 in words is "twenty million, four hundred four thousand, four hundred twenty-one".