21168987 has 16 divisors (see below), whose sum is σ = 32562432. Its totient is φ = 11982240.

The previous prime is 21168977. The next prime is 21169007. The reversal of 21168987 is 78986112.

It is not a de Polignac number, because 21168987 - 2⁴ = 21168971 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21168967) 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 in 15 ways as a sum of consecutive naturals, for example, 2464 + ... + 6957.

It is an arithmetic number, because the mean of its divisors is an integer number (2035152).

Almost surely, 2^21168987 is an apocalyptic number.

21168987 is a deficient number, since it is larger than the sum of its proper divisors (11393445).

21168987 is a wasteful number, since it uses less digits than its factorization.

21168987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9538.

The product of its digits is 48384, while the sum is 42.

The square root of 21168987 is about 4600.9767441273. The cubic root of 21168987 is about 276.6304768715.

It can be divided in two parts, 21168 and 987, that added together give a triangular number (22155 = T₂₁₀).

The spelling of 21168987 in words is "twenty-one million, one hundred sixty-eight thousand, nine hundred eighty-seven".