21309386 has 16 divisors (see below), whose sum is σ = 36590400. Its totient is φ = 9117600.

The previous prime is 21309383. The next prime is 21309397. The reversal of 21309386 is 68390312.

It is not an unprimeable number, because it can be changed into a prime (21309383) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13961 + ... + 15411.

It is an arithmetic number, because the mean of its divisors is an integer number (2286900).

Almost surely, 2^21309386 is an apocalyptic number.

21309386 is a deficient number, since it is larger than the sum of its proper divisors (15281014).

21309386 is a wasteful number, since it uses less digits than its factorization.

21309386 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2509.

The product of its (nonzero) digits is 7776, while the sum is 32.

The square root of 21309386 is about 4616.2090507255. The cubic root of 21309386 is about 277.2406949257.

Adding to 21309386 its reverse (68390312), we get a palindrome (89699698).

The spelling of 21309386 in words is "twenty-one million, three hundred nine thousand, three hundred eighty-six".