21533420 has 12 divisors (see below), whose sum is σ = 45220224. Its totient is φ = 8613360.

The previous prime is 21533363. The next prime is 21533431. The reversal of 21533420 is 2433512.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (20), and also a Moran number because the ratio is a prime number: 1076671 = 21533420 / (2 + 1 + 5 + 3 + 3 + 4 + 2 + 0).

It is a junction number, because it is equal to n+sod(n) for n = 21533392 and 21533401.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 538316 + ... + 538355.

It is an arithmetic number, because the mean of its divisors is an integer number (3768352).

Almost surely, 2^21533420 is an apocalyptic number.

21533420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21533420 is an abundant number, since it is smaller than the sum of its proper divisors (23686804).

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

21533420 is a wasteful number, since it uses less digits than its factorization.

21533420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1076680 (or 1076678 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 20.

The square root of 21533420 is about 4640.4116196734. The cubic root of 21533420 is about 278.2088901507.

Adding to 21533420 its reverse (2433512), we get a palindrome (23966932).

The spelling of 21533420 in words is "twenty-one million, five hundred thirty-three thousand, four hundred twenty".