21533445 has 48 divisors (see below), whose sum is σ = 39836160. Its totient is φ = 11150784.

The previous prime is 21533443. The next prime is 21533459. The reversal of 21533445 is 54433512.

21533445 is a `hidden beast` number, since 215 + 3 + 3 + 445 = 666.

It is not a de Polignac number, because 21533445 - 2¹ = 21533443 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21533443) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 44716 + ... + 45194.

It is an arithmetic number, because the mean of its divisors is an integer number (829920).

Almost surely, 2^21533445 is an apocalyptic number.

It is an amenable number.

21533445 is a deficient number, since it is larger than the sum of its proper divisors (18302715).

21533445 is an equidigital number, since it uses as much as digits as its factorization.

21533445 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 536 (or 524 counting only the distinct ones).

The product of its digits is 7200, while the sum is 27.

The square root of 21533445 is about 4640.4143133992. The cubic root of 21533445 is about 278.2089978162.

Adding to 21533445 its reverse (54433512), we get a palindrome (75966957).

The spelling of 21533445 in words is "twenty-one million, five hundred thirty-three thousand, four hundred forty-five".