21309392 has 40 divisors (see below), whose sum is σ = 45325224. Its totient is φ = 9644544.

The previous prime is 21309383. The next prime is 21309397. The reversal of 21309392 is 29390312.

It can be written as a sum of positive squares in 4 ways, for example, as 3297856 + 18011536 = 1816^2 + 4244^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21309397) 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 7 ways as a sum of consecutive naturals, for example, 10058 + ... + 11990.

Almost surely, 2^21309392 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21309392, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22662612).

21309392 is an abundant number, since it is smaller than the sum of its proper divisors (24015832).

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

21309392 is a wasteful number, since it uses less digits than its factorization.

21309392 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2007 (or 2001 counting only the distinct ones).

The product of its (nonzero) digits is 2916, while the sum is 29.

The square root of 21309392 is about 4616.2097006094. The cubic root of 21309392 is about 277.2407209462.

The spelling of 21309392 in words is "twenty-one million, three hundred nine thousand, three hundred ninety-two".