21806012 has 6 divisors (see below), whose sum is σ = 38160528. Its totient is φ = 10903004.

The previous prime is 21806011. The next prime is 21806023. The reversal of 21806012 is 21060812.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21806011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2725748 + ... + 2725755.

It is an arithmetic number, because the mean of its divisors is an integer number (6360088).

Almost surely, 2^21806012 is an apocalyptic number.

It is an amenable number.

21806012 is a deficient number, since it is larger than the sum of its proper divisors (16354516).

21806012 is a wasteful number, since it uses less digits than its factorization.

21806012 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5451507 (or 5451505 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 21806012 is about 4669.6907820540. The cubic root of 21806012 is about 279.3779216680.

Adding to 21806012 its reverse (21060812), we get a palindrome (42866824).

It can be divided in two parts, 2180 and 6012, that added together give a 13-th power (8192 = 2¹³).

The spelling of 21806012 in words is "twenty-one million, eight hundred six thousand, twelve".