21391106 has 24 divisors (see below), whose sum is σ = 36237180. Its totient is φ = 9456480.

The previous prime is 21391091. The next prime is 21391129. The reversal of 21391106 is 60119312.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 21242881 + 148225 = 4609^2 + 385^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7760 + ... + 10148.

Almost surely, 2^21391106 is an apocalyptic number.

21391106 is a deficient number, since it is larger than the sum of its proper divisors (14846074).

21391106 is a wasteful number, since it uses less digits than its factorization.

21391106 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2450 (or 2439 counting only the distinct ones).

The product of its (nonzero) digits is 324, while the sum is 23.

The square root of 21391106 is about 4625.0519997077. The cubic root of 21391106 is about 277.5946423929.

It can be divided in two parts, 213 and 91106, that added together give a palindrome (91319).

The spelling of 21391106 in words is "twenty-one million, three hundred ninety-one thousand, one hundred six".