21868839 has 16 divisors (see below), whose sum is σ = 32509440. Its totient is φ = 14529240.

The previous prime is 21868831. The next prime is 21868841. The reversal of 21868839 is 93886812.

It is not a de Polignac number, because 21868839 - 2³ = 21868831 is a prime.

It is a super-2 number, since 2×21868839² = 956492238415842, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21868794 and 21868803.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21868831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7714 + ... + 10160.

It is an arithmetic number, because the mean of its divisors is an integer number (2031840).

Almost surely, 2^21868839 is an apocalyptic number.

21868839 is a deficient number, since it is larger than the sum of its proper divisors (10640601).

21868839 is a wasteful number, since it uses less digits than its factorization.

21868839 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2787 (or 2781 counting only the distinct ones).

The product of its digits is 165888, while the sum is 45.

The square root of 21868839 is about 4676.4130484806. The cubic root of 21868839 is about 279.6459768928.

It can be divided in two parts, 2186 and 8839, that added together give a square (11025 = 105²).

The spelling of 21868839 in words is "twenty-one million, eight hundred sixty-eight thousand, eight hundred thirty-nine".