21909212 has 12 divisors (see below), whose sum is σ = 41290536. Its totient is φ = 10111920.

The previous prime is 21909169. The next prime is 21909227. The reversal of 21909212 is 21290912.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (26).

It is a congruent 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, 210614 + ... + 210717.

It is an arithmetic number, because the mean of its divisors is an integer number (3440878).

Almost surely, 2^21909212 is an apocalyptic number.

It is an amenable number.

21909212 is a deficient number, since it is larger than the sum of its proper divisors (19381324).

21909212 is a wasteful number, since it uses less digits than its factorization.

21909212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 421348 (or 421346 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 26.

The square root of 21909212 is about 4680.7277211989. The cubic root of 21909212 is about 279.8179599048.

The spelling of 21909212 in words is "twenty-one million, nine hundred nine thousand, two hundred twelve".