21806156 has 12 divisors (see below), whose sum is σ = 38372880. Its totient is φ = 10842480.

The previous prime is 21806149. The next prime is 21806177. The reversal of 21806156 is 65160812.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14336 + ... + 15783.

It is an arithmetic number, because the mean of its divisors is an integer number (3197740).

Almost surely, 2^21806156 is an apocalyptic number.

It is an amenable number.

21806156 is a deficient number, since it is larger than the sum of its proper divisors (16566724).

21806156 is a wasteful number, since it uses less digits than its factorization.

21806156 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30304 (or 30302 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 29.

The square root of 21806156 is about 4669.7062006083. The cubic root of 21806156 is about 279.3785366411.

Adding to 21806156 its reverse (65160812), we get a palindrome (86966968).

The spelling of 21806156 in words is "twenty-one million, eight hundred six thousand, one hundred fifty-six".