21138012 has 108 divisors (see below), whose sum is σ = 64982736. Its totient is φ = 5765760.

The previous prime is 21138011. The next prime is 21138017. The reversal of 21138012 is 21083112.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21138011) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 40312 + ... + 40832.

It is an arithmetic number, because the mean of its divisors is an integer number (601692).

Almost surely, 2^21138012 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 21138012, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32491368).

21138012 is an abundant number, since it is smaller than the sum of its proper divisors (43844724).

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

21138012 is a wasteful number, since it uses less digits than its factorization.

21138012 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 568 (or 556 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 18.

The square root of 21138012 is about 4597.6093787968. The cubic root of 21138012 is about 276.4954867607.

The spelling of 21138012 in words is "twenty-one million, one hundred thirty-eight thousand, twelve".