21653445 has 32 divisors (see below), whose sum is σ = 39790080. Its totient is φ = 9944640.

The previous prime is 21653441. The next prime is 21653447. The reversal of 21653445 is 54435612.

It is not a de Polignac number, because 21653445 - 2² = 21653441 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21653441) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 319 + ... + 6588.

It is an arithmetic number, because the mean of its divisors is an integer number (1243440).

Almost surely, 2^21653445 is an apocalyptic number.

It is an amenable number.

21653445 is a deficient number, since it is larger than the sum of its proper divisors (18136635).

21653445 is a wasteful number, since it uses less digits than its factorization.

21653445 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6945.

The product of its digits is 14400, while the sum is 30.

The square root of 21653445 is about 4653.3262296985. The cubic root of 21653445 is about 278.7248350130.

The spelling of 21653445 in words is "twenty-one million, six hundred fifty-three thousand, four hundred forty-five".