21865291 has 8 divisors (see below), whose sum is σ = 25219040. Its totient is φ = 18569088.

The previous prime is 21865289. The next prime is 21865331. The reversal of 21865291 is 19256812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21865291 - 2¹ = 21865289 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21865211) 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 7 ways as a sum of consecutive naturals, for example, 13566 + ... + 15091.

It is an arithmetic number, because the mean of its divisors is an integer number (3152380).

Almost surely, 2^21865291 is an apocalyptic number.

21865291 is a deficient number, since it is larger than the sum of its proper divisors (3353749).

21865291 is a wasteful number, since it uses less digits than its factorization.

21865291 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28773.

The product of its digits is 8640, while the sum is 34.

The square root of 21865291 is about 4676.0336825134. The cubic root of 21865291 is about 279.6308528223.

The spelling of 21865291 in words is "twenty-one million, eight hundred sixty-five thousand, two hundred ninety-one".