21212736 has 112 divisors (see below), whose sum is σ = 60935616. Its totient is φ = 6488064.

The previous prime is 21212731. The next prime is 21212749. The reversal of 21212736 is 63721212.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is not an unprimeable number, because it can be changed into a prime (21212731) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 218640 + ... + 218736.

It is an arithmetic number, because the mean of its divisors is an integer number (544068).

Almost surely, 2^21212736 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 21212736, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30467808).

21212736 is an abundant number, since it is smaller than the sum of its proper divisors (39722880).

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

21212736 is a wasteful number, since it uses less digits than its factorization.

21212736 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 196 (or 186 counting only the distinct ones).

The product of its digits is 1008, while the sum is 24.

The square root of 21212736 is about 4605.7286068547. The cubic root of 21212736 is about 276.8209123608.

Adding to 21212736 its reverse (63721212), we get a palindrome (84933948).

The spelling of 21212736 in words is "twenty-one million, two hundred twelve thousand, seven hundred thirty-six".