21890689 has 2 divisors, whose sum is σ = 21890690. Its totient is φ = 21890688.

The previous prime is 21890677. The next prime is 21890719. The reversal of 21890689 is 98609812.

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., 17514225 + 4376464 = 4185^2 + 2092^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21890689 is a prime.

It is not a weakly prime, because it can be changed into another prime (21890629) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10945344 + 10945345.

It is an arithmetic number, because the mean of its divisors is an integer number (10945345).

Almost surely, 2^21890689 is an apocalyptic number.

It is an amenable number.

21890689 is a deficient number, since it is larger than the sum of its proper divisors (1).

21890689 is an equidigital number, since it uses as much as digits as its factorization.

21890689 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 62208, while the sum is 43.

The square root of 21890689 is about 4678.7486574938. The cubic root of 21890689 is about 279.7390809167.

The spelling of 21890689 in words is "twenty-one million, eight hundred ninety thousand, six hundred eighty-nine".