21986289 has 16 divisors (see below), whose sum is σ = 35078400. Its totient is φ = 13529808.

The previous prime is 21986273. The next prime is 21986309. The reversal of 21986289 is 98268912.

21986289 is a `hidden beast` number, since 2 + 19 + 8 + 628 + 9 = 666.

It is not a de Polignac number, because 21986289 - 2⁴ = 21986273 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21986269) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 30969 + ... + 31670.

It is an arithmetic number, because the mean of its divisors is an integer number (2192400).

Almost surely, 2^21986289 is an apocalyptic number.

It is an amenable number.

21986289 is a deficient number, since it is larger than the sum of its proper divisors (13092111).

21986289 is a wasteful number, since it uses less digits than its factorization.

21986289 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62661 (or 62655 counting only the distinct ones).

The product of its digits is 124416, while the sum is 45.

The square root of 21986289 is about 4688.9539345146. The cubic root of 21986289 is about 280.1457107243.

It can be divided in two parts, 21 and 986289, that added together give a triangular number (986310 = T₁₄₀₄).

The spelling of 21986289 in words is "twenty-one million, nine hundred eighty-six thousand, two hundred eighty-nine".