1240420021 has 2 divisors, whose sum is σ = 1240420022. Its totient is φ = 1240420020.

The previous prime is 1240419991. The next prime is 1240420033. The reversal of 1240420021 is 1200240421.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1121915025 + 118504996 = 33495^2 + 10886^2 .

It is a cyclic number.

It is not a de Polignac number, because 1240420021 - 2⁷ = 1240419893 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1240419977 and 1240420004.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1240420091) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 620210010 + 620210011.

It is an arithmetic number, because the mean of its divisors is an integer number (620210011).

Almost surely, 2^1240420021 is an apocalyptic number.

It is an amenable number.

1240420021 is a deficient number, since it is larger than the sum of its proper divisors (1).

1240420021 is an equidigital number, since it uses as much as digits as its factorization.

1240420021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 128, while the sum is 16.

The square root of 1240420021 is about 35219.5971158104. The cubic root of 1240420021 is about 1074.4583594812.

Adding to 1240420021 its reverse (1200240421), we get a palindrome (2440660442).

The spelling of 1240420021 in words is "one billion, two hundred forty million, four hundred twenty thousand, twenty-one".