21005112 has 16 divisors (see below), whose sum is σ = 52512840. Its totient is φ = 7001696.

The previous prime is 21005111. The next prime is 21005123. The reversal of 21005112 is 21150012.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21005111) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 437583 + ... + 437630.

Almost surely, 2^21005112 is an apocalyptic number.

It is an amenable number.

21005112 is an abundant number, since it is smaller than the sum of its proper divisors (31507728).

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

21005112 is a wasteful number, since it uses less digits than its factorization.

21005112 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 875222 (or 875218 counting only the distinct ones).

The product of its (nonzero) digits is 20, while the sum is 12.

The square root of 21005112 is about 4583.1334259434. The cubic root of 21005112 is about 275.9148025209.

Adding to 21005112 its reverse (21150012), we get a palindrome (42155124).

The spelling of 21005112 in words is "twenty-one million, five thousand, one hundred twelve".