21197545 has 4 divisors (see below), whose sum is σ = 25437060. Its totient is φ = 16958032.

The previous prime is 21197489. The next prime is 21197551. The reversal of 21197545 is 54579112.

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 7750656 + 13446889 = 2784^2 + 3667^2 .

It is a cyclic number.

It is not a de Polignac number, because 21197545 - 2¹¹ = 21195497 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21197545.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 2119750 + ... + 2119759.

It is an arithmetic number, because the mean of its divisors is an integer number (6359265).

Almost surely, 2^21197545 is an apocalyptic number.

It is an amenable number.

21197545 is a deficient number, since it is larger than the sum of its proper divisors (4239515).

21197545 is an equidigital number, since it uses as much as digits as its factorization.

21197545 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4239514.

The product of its digits is 12600, while the sum is 34.

The square root of 21197545 is about 4604.0791696060. The cubic root of 21197545 is about 276.7548169941.

The spelling of 21197545 in words is "twenty-one million, one hundred ninety-seven thousand, five hundred forty-five".