21688049 has 2 divisors, whose sum is σ = 21688050. Its totient is φ = 21688048.

The previous prime is 21688013. The next prime is 21688067. The reversal of 21688049 is 94088612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21687649 + 400 = 4657^2 + 20^2 .

It is a cyclic number.

It is not a de Polignac number, because 21688049 - 2⁸ = 21687793 is a prime.

It is not a weakly prime, because it can be changed into another prime (21688649) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10844024 + 10844025.

It is an arithmetic number, because the mean of its divisors is an integer number (10844025).

Almost surely, 2^21688049 is an apocalyptic number.

It is an amenable number.

21688049 is a deficient number, since it is larger than the sum of its proper divisors (1).

21688049 is an equidigital number, since it uses as much as digits as its factorization.

21688049 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 27648, while the sum is 38.

The square root of 21688049 is about 4657.0429459046. The cubic root of 21688049 is about 278.8732311214.

The spelling of 21688049 in words is "twenty-one million, six hundred eighty-eight thousand, forty-nine".