21318889 has 2 divisors, whose sum is σ = 21318890. Its totient is φ = 21318888.

The previous prime is 21318881. The next prime is 21318911. The reversal of 21318889 is 98881312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19713600 + 1605289 = 4440^2 + 1267^2 .

It is a cyclic number.

It is not a de Polignac number, because 21318889 - 2³ = 21318881 is a prime.

It is not a weakly prime, because it can be changed into another prime (21318881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10659444 + 10659445.

It is an arithmetic number, because the mean of its divisors is an integer number (10659445).

Almost surely, 2^21318889 is an apocalyptic number.

It is an amenable number.

21318889 is a deficient number, since it is larger than the sum of its proper divisors (1).

21318889 is an equidigital number, since it uses as much as digits as its factorization.

21318889 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27648, while the sum is 40.

The square root of 21318889 is about 4617.2382437990. The cubic root of 21318889 is about 277.2819009742.

The spelling of 21318889 in words is "twenty-one million, three hundred eighteen thousand, eight hundred eighty-nine".