21180545 has 4 divisors (see below), whose sum is σ = 25416660. Its totient is φ = 16944432.

The previous prime is 21180529. The next prime is 21180571. The reversal of 21180545 is 54508112.

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 4566769 + 16613776 = 2137^2 + 4076^2 .

It is a cyclic number.

It is not a de Polignac number, because 21180545 - 2⁴ = 21180529 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2118050 + ... + 2118059.

It is an arithmetic number, because the mean of its divisors is an integer number (6354165).

Almost surely, 2^21180545 is an apocalyptic number.

It is an amenable number.

21180545 is a deficient number, since it is larger than the sum of its proper divisors (4236115).

21180545 is an equidigital number, since it uses as much as digits as its factorization.

21180545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4236114.

The product of its (nonzero) digits is 1600, while the sum is 26.

The square root of 21180545 is about 4602.2326103751. The cubic root of 21180545 is about 276.6808132958.

Adding to 21180545 its reverse (54508112), we get a palindrome (75688657).

The spelling of 21180545 in words is "twenty-one million, one hundred eighty thousand, five hundred forty-five".