21573645 has 32 divisors (see below), whose sum is σ = 36979200. Its totient is φ = 10707264.

The previous prime is 21573637. The next prime is 21573647. The reversal of 21573645 is 54637512.

It is not a de Polignac number, because 21573645 - 2³ = 21573637 is a prime.

It is a super-3 number, since 3×21573645³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21573647) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 16174 + ... + 17456.

It is an arithmetic number, because the mean of its divisors is an integer number (1155600).

Almost surely, 2^21573645 is an apocalyptic number.

It is an amenable number.

21573645 is a deficient number, since it is larger than the sum of its proper divisors (15405555).

21573645 is a wasteful number, since it uses less digits than its factorization.

21573645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1369.

The product of its digits is 25200, while the sum is 33.

The square root of 21573645 is about 4644.7438034837. The cubic root of 21573645 is about 278.3820162572.

The spelling of 21573645 in words is "twenty-one million, five hundred seventy-three thousand, six hundred forty-five".