21906887 has 2 divisors, whose sum is σ = 21906888. Its totient is φ = 21906886.

The previous prime is 21906883. The next prime is 21906889. The reversal of 21906887 is 78860912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21906887 - 2² = 21906883 is a prime.

Together with 21906889, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21906883) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10953443 + 10953444.

It is an arithmetic number, because the mean of its divisors is an integer number (10953444).

Almost surely, 2^21906887 is an apocalyptic number.

21906887 is a deficient number, since it is larger than the sum of its proper divisors (1).

21906887 is an equidigital number, since it uses as much as digits as its factorization.

21906887 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48384, while the sum is 41.

The square root of 21906887 is about 4680.4793557925. The cubic root of 21906887 is about 279.8080614844.

The spelling of 21906887 in words is "twenty-one million, nine hundred six thousand, eight hundred eighty-seven".