21989237 has 2 divisors, whose sum is σ = 21989238. Its totient is φ = 21989236.

The previous prime is 21989207. The next prime is 21989269. The reversal of 21989237 is 73298912.

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., 19989841 + 1999396 = 4471^2 + 1414^2 .

It is a cyclic number.

It is not a de Polignac number, because 21989237 - 2¹⁸ = 21727093 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21989194 and 21989203.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21989207) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10994618 + 10994619.

It is an arithmetic number, because the mean of its divisors is an integer number (10994619).

Almost surely, 2^21989237 is an apocalyptic number.

It is an amenable number.

21989237 is a deficient number, since it is larger than the sum of its proper divisors (1).

21989237 is an equidigital number, since it uses as much as digits as its factorization.

21989237 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 54432, while the sum is 41.

The square root of 21989237 is about 4689.2682798066. The cubic root of 21989237 is about 280.1582311432.

The spelling of 21989237 in words is "twenty-one million, nine hundred eighty-nine thousand, two hundred thirty-seven".