21878243 has 2 divisors, whose sum is σ = 21878244. Its totient is φ = 21878242.

The previous prime is 21878149. The next prime is 21878251. The reversal of 21878243 is 34287812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21878243 - 2¹² = 21874147 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21878293) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10939121 + 10939122.

It is an arithmetic number, because the mean of its divisors is an integer number (10939122).

Almost surely, 2^21878243 is an apocalyptic number.

21878243 is a deficient number, since it is larger than the sum of its proper divisors (1).

21878243 is an equidigital number, since it uses as much as digits as its factorization.

21878243 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 21504, while the sum is 35.

The square root of 21878243 is about 4677.4184119020. The cubic root of 21878243 is about 279.6860554402.

The spelling of 21878243 in words is "twenty-one million, eight hundred seventy-eight thousand, two hundred forty-three".