21994237 has 2 divisors, whose sum is σ = 21994238. Its totient is φ = 21994236.

The previous prime is 21994213. The next prime is 21994319. The reversal of 21994237 is 73249912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14092516 + 7901721 = 3754^2 + 2811^2 .

It is a cyclic number.

It is not a de Polignac number, because 21994237 - 2¹¹ = 21992189 is a prime.

It is a super-2 number, since 2×21994237² = 967492922424338, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21994196 and 21994205.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21997237) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10997118 + 10997119.

It is an arithmetic number, because the mean of its divisors is an integer number (10997119).

Almost surely, 2^21994237 is an apocalyptic number.

It is an amenable number.

21994237 is a deficient number, since it is larger than the sum of its proper divisors (1).

21994237 is an equidigital number, since it uses as much as digits as its factorization.

21994237 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 27216, while the sum is 37.

The square root of 21994237 is about 4689.8013817218. The cubic root of 21994237 is about 280.1794640308.

The spelling of 21994237 in words is "twenty-one million, nine hundred ninety-four thousand, two hundred thirty-seven".