21819841 has 2 divisors, whose sum is σ = 21819842. Its totient is φ = 21819840.

The previous prime is 21819821. The next prime is 21819869. The reversal of 21819841 is 14891812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21818241 + 1600 = 4671^2 + 40^2 .

It is a cyclic number.

It is not a de Polignac number, because 21819841 - 2⁷ = 21819713 is a prime.

It is a super-2 number, since 2×21819841² = 952210922530562, which contains 22 as substring.

It is equal to p_1378537 and since 21819841 and 1378537 have the same sum of digits, it is a Honaker prime.

It is a junction number, because it is equal to n+sod(n) for n = 21819797 and 21819806.

It is not a weakly prime, because it can be changed into another prime (21819821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10909920 + 10909921.

It is an arithmetic number, because the mean of its divisors is an integer number (10909921).

Almost surely, 2^21819841 is an apocalyptic number.

It is an amenable number.

21819841 is a deficient number, since it is larger than the sum of its proper divisors (1).

21819841 is an equidigital number, since it uses as much as digits as its factorization.

21819841 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4608, while the sum is 34.

The square root of 21819841 is about 4671.1712663956. The cubic root of 21819841 is about 279.4369680882.

The spelling of 21819841 in words is "twenty-one million, eight hundred nineteen thousand, eight hundred forty-one".