21878567 has 2 divisors, whose sum is σ = 21878568. Its totient is φ = 21878566.

The previous prime is 21878531. The next prime is 21878569. The reversal of 21878567 is 76587812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21878567 - 2¹² = 21874471 is a prime.

Together with 21878569, it forms a pair of twin primes.

It is a Chen prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21878569) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10939283 + 10939284.

It is an arithmetic number, because the mean of its divisors is an integer number (10939284).

Almost surely, 2^21878567 is an apocalyptic number.

21878567 is a deficient number, since it is larger than the sum of its proper divisors (1).

21878567 is an equidigital number, since it uses as much as digits as its factorization.

21878567 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 188160, while the sum is 44.

The square root of 21878567 is about 4677.4530462635. The cubic root of 21878567 is about 279.6874360788.

The spelling of 21878567 in words is "twenty-one million, eight hundred seventy-eight thousand, five hundred sixty-seven".