21023545 has 4 divisors (see below), whose sum is σ = 25228260. Its totient is φ = 16818832.

The previous prime is 21023533. The next prime is 21023573. The reversal of 21023545 is 54532012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16426809 + 4596736 = 4053^2 + 2144^2 .

It is a cyclic number.

It is not a de Polignac number, because 21023545 - 2⁷ = 21023417 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2102350 + ... + 2102359.

It is an arithmetic number, because the mean of its divisors is an integer number (6307065).

Almost surely, 2^21023545 is an apocalyptic number.

It is an amenable number.

21023545 is a deficient number, since it is larger than the sum of its proper divisors (4204715).

21023545 is an equidigital number, since it uses as much as digits as its factorization.

21023545 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4204714.

The product of its (nonzero) digits is 1200, while the sum is 22.

The square root of 21023545 is about 4585.1439453958. The cubic root of 21023545 is about 275.9954884441.

Adding to 21023545 its reverse (54532012), we get a palindrome (75555557).

The spelling of 21023545 in words is "twenty-one million, twenty-three thousand, five hundred forty-five".