21012420 has 192 divisors, whose sum is σ = 72253440. Its totient is φ = 4492800.

The previous prime is 21012419. The next prime is 21012421. The reversal of 21012420 is 2421012.

It is an interprime number because it is at equal distance from previous prime (21012419) and next prime (21012421).

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

It is a junction number, because it is equal to n+sod(n) for n = 21012396 and 21012405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012421) by changing a digit.

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 63 ways as a sum of consecutive naturals, for example, 265941 + ... + 266019.

It is an arithmetic number, because the mean of its divisors is an integer number (376320).

Almost surely, 2^21012420 is an apocalyptic number.

21012420 is a gapful number since it is divisible by the number (20) 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 21012420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36126720).

21012420 is an abundant number, since it is smaller than the sum of its proper divisors (51241020).

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

21012420 is a wasteful number, since it uses less digits than its factorization.

21012420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 146 (or 144 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 12.

The square root of 21012420 is about 4583.9306277473. The cubic root of 21012420 is about 275.9467971385.

Adding to 21012420 its reverse (2421012), we get a palindrome (23433432).

The spelling of 21012420 in words is "twenty-one million, twelve thousand, four hundred twenty".