21890369 has 2 divisors, whose sum is σ = 21890370. Its totient is φ = 21890368.

The previous prime is 21890329. The next prime is 21890377. The reversal of 21890369 is 96309812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16507969 + 5382400 = 4063^2 + 2320^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21890369 is a prime.

It is a super-2 number, since 2×21890369² = 958376509912322, which contains 22 as substring.

It is a Chen prime.

It is an alternating number because its digits alternate between even and odd.

It is not a weakly prime, because it can be changed into another prime (21890329) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10945184 + 10945185.

It is an arithmetic number, because the mean of its divisors is an integer number (10945185).

Almost surely, 2^21890369 is an apocalyptic number.

It is an amenable number.

21890369 is a deficient number, since it is larger than the sum of its proper divisors (1).

21890369 is an equidigital number, since it uses as much as digits as its factorization.

21890369 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 23328, while the sum is 38.

The square root of 21890369 is about 4678.7144601910. The cubic root of 21890369 is about 279.7377178266.

The spelling of 21890369 in words is "twenty-one million, eight hundred ninety thousand, three hundred sixty-nine".