21651841 has 2 divisors, whose sum is σ = 21651842. Its totient is φ = 21651840.

The previous prime is 21651823. The next prime is 21651853. The reversal of 21651841 is 14815612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18662400 + 2989441 = 4320^2 + 1729^2 .

It is a cyclic number.

It is not a de Polignac number, because 21651841 - 2²³ = 13263233 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21651881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10825920 + 10825921.

It is an arithmetic number, because the mean of its divisors is an integer number (10825921).

Almost surely, 2^21651841 is an apocalyptic number.

It is an amenable number.

21651841 is a deficient number, since it is larger than the sum of its proper divisors (1).

21651841 is an equidigital number, since it uses as much as digits as its factorization.

21651841 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1920, while the sum is 28.

The square root of 21651841 is about 4653.1538766733. The cubic root of 21651841 is about 278.7179525719.

The spelling of 21651841 in words is "twenty-one million, six hundred fifty-one thousand, eight hundred forty-one".