21533645 has 16 divisors (see below), whose sum is σ = 31269888. Its totient is φ = 13896960.

The previous prime is 21533597. The next prime is 21533647. The reversal of 21533645 is 54633512.

It is not a de Polignac number, because 21533645 - 2⁶ = 21533581 is a prime.

It is a super-3 number, since 3×21533645³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21533647) 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, 17501 + ... + 18690.

It is an arithmetic number, because the mean of its divisors is an integer number (1954368).

Almost surely, 2^21533645 is an apocalyptic number.

It is an amenable number.

21533645 is a deficient number, since it is larger than the sum of its proper divisors (9736243).

21533645 is a wasteful number, since it uses less digits than its factorization.

21533645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36220.

The product of its digits is 10800, while the sum is 29.

The square root of 21533645 is about 4640.4358631491. The cubic root of 21533645 is about 278.2098591372.

The spelling of 21533645 in words is "twenty-one million, five hundred thirty-three thousand, six hundred forty-five".