21865842 has 32 divisors (see below), whose sum is σ = 51451200. Its totient is φ = 6859584.

The previous prime is 21865841. The next prime is 21865843. The reversal of 21865842 is 24856812.

It is an interprime number because it is at equal distance from previous prime (21865841) and next prime (21865843).

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 21865797 and 21865806.

It is not an unprimeable number, because it can be changed into a prime (21865841) 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, 10992 + ... + 12827.

It is an arithmetic number, because the mean of its divisors is an integer number (1607850).

Almost surely, 2^21865842 is an apocalyptic number.

21865842 is an abundant number, since it is smaller than the sum of its proper divisors (29585358).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21865842 is a wasteful number, since it uses less digits than its factorization.

21865842 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23847 (or 23841 counting only the distinct ones).

The product of its digits is 30720, while the sum is 36.

The square root of 21865842 is about 4676.0925995964. The cubic root of 21865842 is about 279.6332016790.

The spelling of 21865842 in words is "twenty-one million, eight hundred sixty-five thousand, eight hundred forty-two".