21955806 has 32 divisors (see below), whose sum is σ = 51662880. Its totient is φ = 6887808.

The previous prime is 21955799. The next prime is 21955807. The reversal of 21955806 is 60855912.

It is a happy number.

It is a congruent 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 (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11041 + ... + 12876.

It is an arithmetic number, because the mean of its divisors is an integer number (1614465).

Almost surely, 2^21955806 is an apocalyptic number.

21955806 is an abundant number, since it is smaller than the sum of its proper divisors (29707074).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21955806 is a wasteful number, since it uses less digits than its factorization.

21955806 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23945 (or 23939 counting only the distinct ones).

The product of its (nonzero) digits is 21600, while the sum is 36.

The square root of 21955806 is about 4685.7022952808. The cubic root of 21955806 is about 280.0161810377.

It can be divided in two parts, 2195 and 5806, that added together give a triangular number (8001 = T₁₂₆).

The spelling of 21955806 in words is "twenty-one million, nine hundred fifty-five thousand, eight hundred six".