21397991449 has 2 divisors, whose sum is σ = 21397991450. Its totient is φ = 21397991448.

The previous prime is 21397991413. The next prime is 21397991453. The reversal of 21397991449 is 94419979312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20993981449 + 404010000 = 144893^2 + 20100^2 .

It is a cyclic number.

It is not a de Polignac number, because 21397991449 - 2⁹ = 21397990937 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21397991393 and 21397991402.

It is not a weakly prime, because it can be changed into another prime (21397991249) 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, 10698995724 + 10698995725.

It is an arithmetic number, because the mean of its divisors is an integer number (10698995725).

Almost surely, 2^21397991449 is an apocalyptic number.

It is an amenable number.

21397991449 is a deficient number, since it is larger than the sum of its proper divisors (1).

21397991449 is an equidigital number, since it uses as much as digits as its factorization.

21397991449 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4408992, while the sum is 58.

The spelling of 21397991449 in words is "twenty-one billion, three hundred ninety-seven million, nine hundred ninety-one thousand, four hundred forty-nine".