21040023449 has 2 divisors, whose sum is σ = 21040023450. Its totient is φ = 21040023448.

The previous prime is 21040023413. The next prime is 21040023517. The reversal of 21040023449 is 94432004012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16433958025 + 4606065424 = 128195^2 + 67868^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21040023449 is a prime.

It is not a weakly prime, because it can be changed into another prime (21040023349) 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, 10520011724 + 10520011725.

It is an arithmetic number, because the mean of its divisors is an integer number (10520011725).

Almost surely, 2^21040023449 is an apocalyptic number.

It is an amenable number.

21040023449 is a deficient number, since it is larger than the sum of its proper divisors (1).

21040023449 is an equidigital number, since it uses as much as digits as its factorization.

21040023449 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6912, while the sum is 29.

The spelling of 21040023449 in words is "twenty-one billion, forty million, twenty-three thousand, four hundred forty-nine".