21678049 has 2 divisors, whose sum is σ = 21678050. Its totient is φ = 21678048.

The previous prime is 21678037. The next prime is 21678061. The reversal of 21678049 is 94087612.

It is a balanced prime because it is at equal distance from previous prime (21678037) and next prime (21678061).

It can be written as a sum of positive squares in only one way, i.e., 14197824 + 7480225 = 3768^2 + 2735^2 .

It is a cyclic number.

It is not a de Polignac number, because 21678049 - 2¹⁹ = 21153761 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21677999 and 21678017.

It is not a weakly prime, because it can be changed into another prime (21688049) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10839024 + 10839025.

It is an arithmetic number, because the mean of its divisors is an integer number (10839025).

Almost surely, 2^21678049 is an apocalyptic number.

It is an amenable number.

21678049 is a deficient number, since it is larger than the sum of its proper divisors (1).

21678049 is an equidigital number, since it uses as much as digits as its factorization.

21678049 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 24192, while the sum is 37.

The square root of 21678049 is about 4655.9691794513. The cubic root of 21678049 is about 278.8303632569.

The spelling of 21678049 in words is "twenty-one million, six hundred seventy-eight thousand, forty-nine".