21270545 has 4 divisors (see below), whose sum is σ = 25524660. Its totient is φ = 17016432.

The previous prime is 21270539. The next prime is 21270547. The reversal of 21270545 is 54507212.

It is a Cunningham number, because it is equal to 4612²+1.

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 7661824 + 13608721 = 2768^2 + 3689^2 .

It is a cyclic number.

It is not a de Polignac number, because 21270545 - 2¹² = 21266449 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21270547) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2127050 + ... + 2127059.

It is an arithmetic number, because the mean of its divisors is an integer number (6381165).

Almost surely, 2^21270545 is an apocalyptic number.

It is an amenable number.

21270545 is a deficient number, since it is larger than the sum of its proper divisors (4254115).

21270545 is an equidigital number, since it uses as much as digits as its factorization.

21270545 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4254114.

The product of its (nonzero) digits is 2800, while the sum is 26.

The square root of 21270545 is about 4612.0001084128. Note that the first 3 decimals coincide. The cubic root of 21270545 is about 277.0721486179.

Adding to 21270545 its reverse (54507212), we get a palindrome (75777757).

The spelling of 21270545 in words is "twenty-one million, two hundred seventy thousand, five hundred forty-five".