21861137 has 2 divisors, whose sum is σ = 21861138. Its totient is φ = 21861136.

The previous prime is 21861127. The next prime is 21861139. The reversal of 21861137 is 73116812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21752896 + 108241 = 4664^2 + 329^2 .

It is a cyclic number.

It is not a de Polignac number, because 21861137 - 2¹⁶ = 21795601 is a prime.

Together with 21861139, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21861139) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10930568 + 10930569.

It is an arithmetic number, because the mean of its divisors is an integer number (10930569).

Almost surely, 2^21861137 is an apocalyptic number.

It is an amenable number.

21861137 is a deficient number, since it is larger than the sum of its proper divisors (1).

21861137 is an equidigital number, since it uses as much as digits as its factorization.

21861137 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2016, while the sum is 29.

The square root of 21861137 is about 4675.5894815520. The cubic root of 21861137 is about 279.6131434745.

Adding to 21861137 its reverse (73116812), we get a palindrome (94977949).

The spelling of 21861137 in words is "twenty-one million, eight hundred sixty-one thousand, one hundred thirty-seven".