21212400 has 120 divisors (see below), whose sum is σ = 74173824. Its totient is φ = 5139200.

The previous prime is 21212353. The next prime is 21212423. The reversal of 21212400 is 421212.

It is a tau number, because it is divible by the number of its divisors (120).

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 12397 + ... + 14003.

Almost surely, 2^21212400 is an apocalyptic number.

21212400 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 21212400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37086912).

21212400 is an abundant number, since it is smaller than the sum of its proper divisors (52961424).

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

21212400 is a wasteful number, since it uses less digits than its factorization.

21212400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1639 (or 1628 counting only the distinct ones).

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

The square root of 21212400 is about 4605.6921303969. The cubic root of 21212400 is about 276.8194507810.

Adding to 21212400 its reverse (421212), we get a palindrome (21633612).

It can be divided in two parts, 21212 and 400, that added together give a palindrome (21612).

The spelling of 21212400 in words is "twenty-one million, two hundred twelve thousand, four hundred".