21747841 has 2 divisors, whose sum is σ = 21747842. Its totient is φ = 21747840.

The previous prime is 21747839. The next prime is 21747871. The reversal of 21747841 is 14874712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20930625 + 817216 = 4575^2 + 904^2 .

It is a cyclic number.

It is not a de Polignac number, because 21747841 - 2¹ = 21747839 is a prime.

It is a super-2 number, since 2×21747841² = 945937176322562, which contains 22 as substring.

Together with 21747839, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21747797 and 21747806.

It is not a weakly prime, because it can be changed into another prime (21747821) 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, 10873920 + 10873921.

It is an arithmetic number, because the mean of its divisors is an integer number (10873921).

Almost surely, 2^21747841 is an apocalyptic number.

It is an amenable number.

21747841 is a deficient number, since it is larger than the sum of its proper divisors (1).

21747841 is an equidigital number, since it uses as much as digits as its factorization.

21747841 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12544, while the sum is 34.

The square root of 21747841 is about 4663.4580517037. The cubic root of 21747841 is about 279.1292721081.

The spelling of 21747841 in words is "twenty-one million, seven hundred forty-seven thousand, eight hundred forty-one".