21381306 has 16 divisors (see below), whose sum is σ = 44622144. Its totient is φ = 6817184.

The previous prime is 21381281. The next prime is 21381307. The reversal of 21381306 is 60318312.

It is not an unprimeable number, because it can be changed into a prime (21381307) 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, 77331 + ... + 77606.

It is an arithmetic number, because the mean of its divisors is an integer number (2788884).

Almost surely, 2^21381306 is an apocalyptic number.

21381306 is an abundant number, since it is smaller than the sum of its proper divisors (23240838).

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

21381306 is a wasteful number, since it uses less digits than its factorization.

21381306 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 154965.

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 21381306 is about 4623.9924307897. The cubic root of 21381306 is about 277.5522440391.

Adding to 21381306 its reverse (60318312), we get a palindrome (81699618).

The spelling of 21381306 in words is "twenty-one million, three hundred eighty-one thousand, three hundred six".