21478841 has 2 divisors, whose sum is σ = 21478842. Its totient is φ = 21478840.

The previous prime is 21478829. The next prime is 21478861. The reversal of 21478841 is 14887412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21114025 + 364816 = 4595^2 + 604^2 .

It is a cyclic number.

It is not a de Polignac number, because 21478841 - 2²² = 17284537 is a prime.

It is a super-2 number, since 2×21478841² = 922681221406562, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is equal to p_1358378 and since 21478841 and 1358378 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21478861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10739420 + 10739421.

It is an arithmetic number, because the mean of its divisors is an integer number (10739421).

Almost surely, 2^21478841 is an apocalyptic number.

It is an amenable number.

21478841 is a deficient number, since it is larger than the sum of its proper divisors (1).

21478841 is an equidigital number, since it uses as much as digits as its factorization.

21478841 is an evil number, because the sum of its binary digits is even.

The product of its digits is 14336, while the sum is 35.

The square root of 21478841 is about 4634.5270524618. The cubic root of 21478841 is about 277.9736401693.

The spelling of 21478841 in words is "twenty-one million, four hundred seventy-eight thousand, eight hundred forty-one".