21806743 has 4 divisors (see below), whose sum is σ = 24922000. Its totient is φ = 18691488.

The previous prime is 21806723. The next prime is 21806749. The reversal of 21806743 is 34760812.

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-21806743 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21806749) 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, 1557618 + ... + 1557631.

It is an arithmetic number, because the mean of its divisors is an integer number (6230500).

Almost surely, 2^21806743 is an apocalyptic number.

21806743 is a deficient number, since it is larger than the sum of its proper divisors (3115257).

21806743 is an equidigital number, since it uses as much as digits as its factorization.

21806743 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3115256.

The product of its (nonzero) digits is 8064, while the sum is 31.

The square root of 21806743 is about 4669.7690521053. The cubic root of 21806743 is about 279.3810434826.

The spelling of 21806743 in words is "twenty-one million, eight hundred six thousand, seven hundred forty-three".