21398849 has 2 divisors, whose sum is σ = 21398850. Its totient is φ = 21398848.

The previous prime is 21398837. The next prime is 21398873. The reversal of 21398849 is 94889312.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15484225 + 5914624 = 3935^2 + 2432^2 .

It is a cyclic number.

It is not a de Polignac number, because 21398849 - 2⁴ = 21398833 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21398899) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10699424 + 10699425.

It is an arithmetic number, because the mean of its divisors is an integer number (10699425).

Almost surely, 2^21398849 is an apocalyptic number.

It is an amenable number.

21398849 is a deficient number, since it is larger than the sum of its proper divisors (1).

21398849 is an equidigital number, since it uses as much as digits as its factorization.

21398849 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 124416, while the sum is 44.

The square root of 21398849 is about 4625.8889956418. Note that the first 3 decimals coincide. The cubic root of 21398849 is about 277.6281322621.

The spelling of 21398849 in words is "twenty-one million, three hundred ninety-eight thousand, eight hundred forty-nine".