21985189 has 2 divisors, whose sum is σ = 21985190. Its totient is φ = 21985188.

The previous prime is 21985153. The next prime is 21985211. The reversal of 21985189 is 98158912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18533025 + 3452164 = 4305^2 + 1858^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21985189 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21985129) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10992594 + 10992595.

It is an arithmetic number, because the mean of its divisors is an integer number (10992595).

Almost surely, 2^21985189 is an apocalyptic number.

It is an amenable number.

21985189 is a deficient number, since it is larger than the sum of its proper divisors (1).

21985189 is an equidigital number, since it uses as much as digits as its factorization.

21985189 is an evil number, because the sum of its binary digits is even.

The product of its digits is 51840, while the sum is 43.

The square root of 21985189 is about 4688.8366360964. The cubic root of 21985189 is about 280.1410386395.

The spelling of 21985189 in words is "twenty-one million, nine hundred eighty-five thousand, one hundred eighty-nine".