21215232420 has 192 divisors, whose sum is σ = 65186257920. Its totient is φ = 5136265728.

The previous prime is 21215232403. The next prime is 21215232421. The reversal of 21215232420 is 2423251212.

It is not an unprimeable number, because it can be changed into a prime (21215232421) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 2822307 + ... + 2829813.

It is an arithmetic number, because the mean of its divisors is an integer number (339511760).

Almost surely, 2^21215232420 is an apocalyptic number.

21215232420 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 21215232420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32593128960).

21215232420 is an abundant number, since it is smaller than the sum of its proper divisors (43971025500).

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

21215232420 is a wasteful number, since it uses less digits than its factorization.

21215232420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7642 (or 7640 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 24.

Adding to 21215232420 its reverse (2423251212), we get a palindrome (23638483632).

The spelling of 21215232420 in words is "twenty-one billion, two hundred fifteen million, two hundred thirty-two thousand, four hundred twenty".