21865617 has 24 divisors (see below), whose sum is σ = 33431424. Its totient is φ = 13742784.

The previous prime is 21865589. The next prime is 21865619. The reversal of 21865617 is 71656812.

It is not a de Polignac number, because 21865617 - 2¹⁶ = 21800081 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21865619) 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 23 ways as a sum of consecutive naturals, for example, 14388 + ... + 15834.

It is an arithmetic number, because the mean of its divisors is an integer number (1392976).

Almost surely, 2^21865617 is an apocalyptic number.

It is an amenable number.

21865617 is a deficient number, since it is larger than the sum of its proper divisors (11565807).

21865617 is a wasteful number, since it uses less digits than its factorization.

21865617 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1549 (or 1546 counting only the distinct ones).

The product of its digits is 20160, while the sum is 36.

The square root of 21865617 is about 4676.0685409861. The cubic root of 21865617 is about 279.6322425318.

The spelling of 21865617 in words is "twenty-one million, eight hundred sixty-five thousand, six hundred seventeen".