21000012 has 48 divisors (see below), whose sum is σ = 55786752. Its totient is φ = 6086080.

The previous prime is 20999999. The next prime is 21000037.

It is a happy number.

21000012 is nontrivially palindromic in base 10.

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 423 + ... + 6494.

It is an arithmetic number, because the mean of its divisors is an integer number (1162224).

Almost surely, 2^21000012 is an apocalyptic number.

21000012 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21000012, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27893376).

21000012 is an abundant number, since it is smaller than the sum of its proper divisors (34786740).

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

21000012 is a wasteful number, since it uses less digits than its factorization.

21000012 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6958 (or 6956 counting only the distinct ones).

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

The square root of 21000012 is about 4582.5770042630. The cubic root of 21000012 is about 275.8924701890.

It can be divided in two parts, 210000 and 12, that added together give a palindrome (210012).

The spelling of 21000012 in words is "twenty-one million, twelve", and thus it is an aban number and an uban number.