21680849 has 2 divisors, whose sum is σ = 21680850. Its totient is φ = 21680848.

The previous prime is 21680833. The next prime is 21680861. The reversal of 21680849 is 94808612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16810000 + 4870849 = 4100^2 + 2207^2 .

It is a cyclic number.

It is not a de Polignac number, because 21680849 - 2⁴ = 21680833 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21680819) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10840424 + 10840425.

It is an arithmetic number, because the mean of its divisors is an integer number (10840425).

Almost surely, 2^21680849 is an apocalyptic number.

It is an amenable number.

21680849 is a deficient number, since it is larger than the sum of its proper divisors (1).

21680849 is an equidigital number, since it uses as much as digits as its factorization.

21680849 is an evil number, because the sum of its binary digits is even.

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

The square root of 21680849 is about 4656.2698590181. The cubic root of 21680849 is about 278.8423675876.

The spelling of 21680849 in words is "twenty-one million, six hundred eighty thousand, eight hundred forty-nine".