20424721 has 2 divisors, whose sum is σ = 20424722. Its totient is φ = 20424720.

The previous prime is 20424707. The next prime is 20424727. The reversal of 20424721 is 12742402.

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., 13242321 + 7182400 = 3639^2 + 2680^2 .

It is a cyclic number.

It is not a de Polignac number, because 20424721 - 2²³ = 12036113 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20424692 and 20424701.

It is not a weakly prime, because it can be changed into another prime (20424727) 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, 10212360 + 10212361.

It is an arithmetic number, because the mean of its divisors is an integer number (10212361).

Almost surely, 2^20424721 is an apocalyptic number.

It is an amenable number.

20424721 is a deficient number, since it is larger than the sum of its proper divisors (1).

20424721 is an equidigital number, since it uses as much as digits as its factorization.

20424721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 896, while the sum is 22.

The square root of 20424721 is about 4519.3717483739. The cubic root of 20424721 is about 273.3497688247.

The spelling of 20424721 in words is "twenty million, four hundred twenty-four thousand, seven hundred twenty-one".