21906036 has 36 divisors (see below), whose sum is σ = 55534752. Its totient is φ = 7280784.

The previous prime is 21906019. The next prime is 21906037. The reversal of 21906036 is 63060912.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21906037) 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 11 ways as a sum of consecutive naturals, for example, 16161 + ... + 17463.

It is an arithmetic number, because the mean of its divisors is an integer number (1542632).

Almost surely, 2^21906036 is an apocalyptic number.

It is an amenable number.

21906036 is an abundant number, since it is smaller than the sum of its proper divisors (33628716).

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

21906036 is a wasteful number, since it uses less digits than its factorization.

21906036 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1780 (or 1775 counting only the distinct ones).

The product of its (nonzero) digits is 1944, while the sum is 27.

The square root of 21906036 is about 4680.3884454178. The cubic root of 21906036 is about 279.8044382746.

Adding to 21906036 its reverse (63060912), we get a palindrome (84966948).

The spelling of 21906036 in words is "twenty-one million, nine hundred six thousand, thirty-six".