21909072 has 20 divisors (see below), whose sum is σ = 56598560. Its totient is φ = 7303008.

The previous prime is 21909029. The next prime is 21909077. The reversal of 21909072 is 27090912.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21909077) 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 3 ways as a sum of consecutive naturals, for example, 228172 + ... + 228267.

It is an arithmetic number, because the mean of its divisors is an integer number (2829928).

Almost surely, 2^21909072 is an apocalyptic number.

It is an amenable number.

21909072 is an abundant number, since it is smaller than the sum of its proper divisors (34689488).

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

21909072 is a wasteful number, since it uses less digits than its factorization.

21909072 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 456450 (or 456444 counting only the distinct ones).

The product of its (nonzero) digits is 2268, while the sum is 30.

The square root of 21909072 is about 4680.7127662355. The cubic root of 21909072 is about 279.8173638907.

Adding to 21909072 its reverse (27090912), we get a palindrome (48999984).

The spelling of 21909072 in words is "twenty-one million, nine hundred nine thousand, seventy-two".