21040024021 has 2 divisors, whose sum is σ = 21040024022. Its totient is φ = 21040024020.

The previous prime is 21040024009. The next prime is 21040024067. The reversal of 21040024021 is 12042004012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17686340100 + 3353683921 = 132990^2 + 57911^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21040024021 is a prime.

It is a super-2 number, since 2×21040024021² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21040023986 and 21040024004.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21040024081) 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, 10520012010 + 10520012011.

It is an arithmetic number, because the mean of its divisors is an integer number (10520012011).

Almost surely, 2^21040024021 is an apocalyptic number.

It is an amenable number.

21040024021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21040024021 is an equidigital number, since it uses as much as digits as its factorization.

21040024021 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.

Adding to 21040024021 its reverse (12042004012), we get a palindrome (33082028033).

The spelling of 21040024021 in words is "twenty-one billion, forty million, twenty-four thousand, twenty-one".