21012 has 24 divisors (see below), whose sum is σ = 52416. Its totient is φ = 6528.

The previous prime is 21011. The next prime is 21013.

It is a happy number.

21012 is nontrivially palindromic in base 10.

21012 is an esthetic number in base 10, because in such base its adjacent digits differ by 1.

It is an interprime number because it is at equal distance from previous prime (21011) and next prime (21013).

It is a Harshad number since it is a multiple of its sum of digits (6).

It is an alternating number because its digits alternate between even and odd.

It is a nialpdrome in base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 153 + ... + 255.

It is an arithmetic number, because the mean of its divisors is an integer number (2184).

2²¹⁰¹² 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 21012, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26208).

21012 is an abundant number, since it is smaller than the sum of its proper divisors (31404).

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

21012 is a wasteful number, since it uses less digits than its factorization.

21012 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 127 (or 125 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 6.

The square root of 21012 is about 144.9551654823. The cubic root of 21012 is about 27.5944958568.

It can be divided in two parts, 210 and 12, that added together give a palindrome (222).

The spelling of 21012 in words is "twenty-one thousand, twelve", and thus it is an iban number.