21170887 has 2 divisors, whose sum is σ = 21170888. Its totient is φ = 21170886.

The previous prime is 21170881. The next prime is 21170909. The reversal of 21170887 is 78807112.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21170887 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21170881) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10585443 + 10585444.

It is an arithmetic number, because the mean of its divisors is an integer number (10585444).

Almost surely, 2^21170887 is an apocalyptic number.

21170887 is a deficient number, since it is larger than the sum of its proper divisors (1).

21170887 is an equidigital number, since it uses as much as digits as its factorization.

21170887 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6272, while the sum is 34.

The square root of 21170887 is about 4601.1832173909. The cubic root of 21170887 is about 276.6387528490.

Adding to 21170887 its reverse (78807112), we get a palindrome (99977999).

The spelling of 21170887 in words is "twenty-one million, one hundred seventy thousand, eight hundred eighty-seven".