21809746 has 8 divisors (see below), whose sum is σ = 37388160. Its totient is φ = 9347028.

The previous prime is 21809743. The next prime is 21809747. The reversal of 21809746 is 64790812.

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

It is not an unprimeable number, because it can be changed into a prime (21809741) 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 3 ways as a sum of consecutive naturals, for example, 778906 + ... + 778933.

It is an arithmetic number, because the mean of its divisors is an integer number (4673520).

Almost surely, 2^21809746 is an apocalyptic number.

21809746 is a deficient number, since it is larger than the sum of its proper divisors (15578414).

21809746 is a wasteful number, since it uses less digits than its factorization.

21809746 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1557848.

The product of its (nonzero) digits is 24192, while the sum is 37.

The square root of 21809746 is about 4670.0905772801. The cubic root of 21809746 is about 279.3938673870.

The spelling of 21809746 in words is "twenty-one million, eight hundred nine thousand, seven hundred forty-six".