21099887 has 2 divisors, whose sum is σ = 21099888. Its totient is φ = 21099886.

The previous prime is 21099863. The next prime is 21099889. The reversal of 21099887 is 78899012.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21099887 is a prime.

Together with 21099889, 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 (21099889) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10549943 + 10549944.

It is an arithmetic number, because the mean of its divisors is an integer number (10549944).

Almost surely, 2^21099887 is an apocalyptic number.

21099887 is a deficient number, since it is larger than the sum of its proper divisors (1).

21099887 is an equidigital number, since it uses as much as digits as its factorization.

21099887 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 72576, while the sum is 44.

The square root of 21099887 is about 4593.4613310661. The cubic root of 21099887 is about 276.3291555347.

The spelling of 21099887 in words is "twenty-one million, ninety-nine thousand, eight hundred eighty-seven".