21545545 has 32 divisors (see below), whose sum is σ = 31968000. Its totient is φ = 13886208.

The previous prime is 21545509. The next prime is 21545551. The reversal of 21545545 is 54554512.

It is not a de Polignac number, because 21545545 - 2²¹ = 19448393 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 28786 + ... + 29524.

It is an arithmetic number, because the mean of its divisors is an integer number (999000).

Almost surely, 2^21545545 is an apocalyptic number.

It is an amenable number.

21545545 is a deficient number, since it is larger than the sum of its proper divisors (10422455).

21545545 is an equidigital number, since it uses as much as digits as its factorization.

21545545 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 782 (or 768 counting only the distinct ones).

The product of its digits is 20000, while the sum is 31.

The square root of 21545545 is about 4641.7178931943. The cubic root of 21545545 is about 278.2610981426.

The spelling of 21545545 in words is "twenty-one million, five hundred forty-five thousand, five hundred forty-five".