21533130 has 48 divisors (see below), whose sum is σ = 56837664. Its totient is φ = 5654880.

The previous prime is 21533123. The next prime is 21533131. The reversal of 21533130 is 3133512.

21533130 is a `hidden beast` number, since 2 + 1 + 533 + 130 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21533131) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4245 + ... + 7815.

It is an arithmetic number, because the mean of its divisors is an integer number (1184118).

Almost surely, 2^21533130 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21533130, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28418832).

21533130 is an abundant number, since it is smaller than the sum of its proper divisors (35304534).

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

21533130 is a wasteful number, since it uses less digits than its factorization.

21533130 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3651 (or 3648 counting only the distinct ones).

The product of its (nonzero) digits is 270, while the sum is 18.

The square root of 21533130 is about 4640.3803723402. The cubic root of 21533130 is about 278.2076412247.

Adding to 21533130 its reverse (3133512), we get a palindrome (24666642).

The spelling of 21533130 in words is "twenty-one million, five hundred thirty-three thousand, one hundred thirty".