21104989 has 2 divisors, whose sum is σ = 21104990. Its totient is φ = 21104988.

The previous prime is 21104981. The next prime is 21104999. The reversal of 21104989 is 98940112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12355225 + 8749764 = 3515^2 + 2958^2 .

It is a cyclic number.

It is not a de Polignac number, because 21104989 - 2³ = 21104981 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21104981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10552494 + 10552495.

It is an arithmetic number, because the mean of its divisors is an integer number (10552495).

Almost surely, 2^21104989 is an apocalyptic number.

It is an amenable number.

21104989 is a deficient number, since it is larger than the sum of its proper divisors (1).

21104989 is an equidigital number, since it uses as much as digits as its factorization.

21104989 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5184, while the sum is 34.

The square root of 21104989 is about 4594.0166521248. The cubic root of 21104989 is about 276.3514260763.

The spelling of 21104989 in words is "twenty-one million, one hundred four thousand, nine hundred eighty-nine".