21955809 has 8 divisors (see below), whose sum is σ = 29296960. Its totient is φ = 14625936.

The previous prime is 21955807. The next prime is 21955831. The reversal of 21955809 is 90855912.

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

It is not a de Polignac number, because 21955809 - 2¹ = 21955807 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21955807) 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 7 ways as a sum of consecutive naturals, for example, 4284 + ... + 7890.

It is an arithmetic number, because the mean of its divisors is an integer number (3662120).

Almost surely, 2^21955809 is an apocalyptic number.

It is an amenable number.

21955809 is a deficient number, since it is larger than the sum of its proper divisors (7341151).

21955809 is a wasteful number, since it uses less digits than its factorization.

21955809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5639.

The product of its (nonzero) digits is 32400, while the sum is 39.

The square root of 21955809 is about 4685.7026154036. The cubic root of 21955809 is about 280.0161937913.

The spelling of 21955809 in words is "twenty-one million, nine hundred fifty-five thousand, eight hundred nine".