21836791 has 4 divisors (see below), whose sum is σ = 21914784. Its totient is φ = 21758800.

The previous prime is 21836779. The next prime is 21836807. The reversal of 21836791 is 19763812.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21836791 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21836791.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21836701) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 38575 + ... + 39136.

It is an arithmetic number, because the mean of its divisors is an integer number (5478696).

Almost surely, 2^21836791 is an apocalyptic number.

21836791 is a deficient number, since it is larger than the sum of its proper divisors (77993).

21836791 is an equidigital number, since it uses as much as digits as its factorization.

21836791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77992.

The product of its digits is 18144, while the sum is 37.

The square root of 21836791 is about 4672.9852343015. The cubic root of 21836791 is about 279.5093063893.

The spelling of 21836791 in words is "twenty-one million, eight hundred thirty-six thousand, seven hundred ninety-one".