21008887 has 2 divisors, whose sum is σ = 21008888. Its totient is φ = 21008886.

The previous prime is 21008879. The next prime is 21008893. The reversal of 21008887 is 78880012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21008887 - 2³ = 21008879 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21008837) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10504443 + 10504444.

It is an arithmetic number, because the mean of its divisors is an integer number (10504444).

Almost surely, 2^21008887 is an apocalyptic number.

21008887 is a deficient number, since it is larger than the sum of its proper divisors (1).

21008887 is an equidigital number, since it uses as much as digits as its factorization.

21008887 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7168, while the sum is 34.

The square root of 21008887 is about 4583.5452435860. The cubic root of 21008887 is about 275.9313304973.

Adding to 21008887 its reverse (78880012), we get a palindrome (99888899).

The spelling of 21008887 in words is "twenty-one million, eight thousand, eight hundred eighty-seven".